In this edition: The electability chorus, the Bernie and Biden wars, and the polls that make us wonder whether we're missing something.

Nobody told me you could just refuse to show up for a hearing, and this is The Trailer.

If you use Flipboard, you can get all of the Trailer "What We Learned" pieces from candidates' early forays here.

DUBUQUE, Iowa — Colleen Kersch, 51, arrived early for Joe Biden's first campaign visit to her city. She took her place in line, wearing a T-shirt that read "A Woman's Place is in the House and the Senate," but she was not pining for a female presidential candidate. She'd been supporting Biden since "before he was cool." The former vice president, she said, could unite the country. 

"As much as I wanted Hillary to win, I had a feeling it would be like it is with Trump," Kersch said. "So many people do not like her. They went after her constantly. It would have been so divisive, and anything she tried to do, Mitch McConnell would have done just what he did to Obama." And Biden? "I think he can stand up to him and give him what he gets back."

In dozens of conversations during Biden's maiden Iowa voyage, some voters said they had been pining for a Biden candidacy. They believed in his experience, and his decency, and his work as vice president. 

Just as many voters said that they had come to support Biden because he seemed best positioned to defeat President Trump — sometimes offering the names of candidates they considered more inspiring but less electable. And several voters struggled to explain why, if he did defeat Trump, Biden would be able to succeed in his agenda where the Obama-Biden administration struggled. 

"I like his honesty and how he wants to get people be united," said Jan Ginter, 65. Asked why the last Democratic administration had not left the country united, Ginter paused for five seconds. "That's tough," she said. "That's a tough one."

More than any other contender for the Democratic nomination, Biden's candidacy is premised on how he can win. No other Democrat comes close. The latest Quinnipiac national poll, which put Biden at 38 percent support among all Democrats, found just 23 percent of them saying Biden had "the best policy ideas." But 56 percent said that Biden had "the best chance of winning," a sentiment shared by every Biden endorser.

"The most important factor that we must determine in the Democratic nomination process is who can win,” Harold Schaitberger, the president of the International Association of Fire Fighters, the only union to make a 2020 endorsement so far, said t Biden's first rally in Pittsburgh. "We can’t have a nominee that’s too far left... a candidate that has high-minded ideals, maybe honorable ideas, but little chance of winning.”

The tautology of the "electability" theory, that Biden is electable because people say he's electable, is a big reason why his entry did not scare off many rival campaigns.

In a March 2007 memo for Hillary Clinton's campaign, pollster Mark Penn warned that Barack Obama was "unelectable except perhaps against Attila the Hun," and at the same time, polls found Democrats saying Clinton was their most electable candidate. In the run-up to the 2004 primary, many Democratic leaders warned that Howard Dean would throw the election and a candidate such as John Kerry would win it.

"The latest polls, as we've all seen, show that John Kerry can defeat George Bush,” Schaitberger said in 2003, after his union endorsed the senator from Massachusetts.

Every recent "electability" debate among Democrats has ended with the "electability" side getting it wrong. That has terrified the party's left, which is always getting the short end of that argument. The notion that the country is too conservative to elect the candidate of the Democratic base is deeply ingrained with both voters and elected Democrats; so is the notion that a candidate who makes voters comfortable, and doesn't challenge their vision of a "traditional" president, is the strongest candidate.

A 2013 academic study of the topic found that legislators thought their constituents were 15 to 20 percent points more conservative on key issues (same-sex marriage, welfare and universal health care) than they really were. That gap is consistent with public polls that ask voters what, in their opinions, their neighbors may be unwilling to vote for; in the Quinnipiac poll, 70 percent of voters say they could support an openly gay candidate for president but only 52 percent say the country is "ready to elect" such a candidate.

Head-to-head polling doesn't move the debate, either, even when it seems to contradict what voters think. In the latest CNN poll, Bernie Sanders runs about as strong in a ballot test with the president as Biden does; Biden gets 51 percent support, and Sanders gets 50 percent. Sanders's campaign pollster has even released internals to emphasize a major campaign argument: that Sanders, who opposed NAFTA and other trade deals that are unpopular in the "Rust Belt," is leading Trump in the key Midwest states. (There are reasons to not overreact to head-to-head polling: Early in the 2015 primary, Donald Trump trailed Hillary Clinton by as much as 15 points in trial heats.)

Both Sanders and Sen. Elizabeth Warren (D-Mass.), the candidates whose "electability" numbers run furthest behind their overall support, have begun to argue that Biden would be a weaker-than-advertised candidate. Warren, who reminds audiences that she was considered the underdog until late in her 2012 race for Senate, has noted that Biden was "on the side of the credit card companies" during regulatory fights before the 2008 crash. Sanders has been sharper, going on CNN and Twitter to emphasize that Biden voted for NAFTA and lobbied for the Trans-Pacific Partnership, both issues that Trump used in 2016 to slice through the Democrats' coalition.

Warren and Sanders, among other candidates, are also sketching out more of a vision for what their presidencies would do, a topic that has been disconnected from "electability." On the stump, Biden has promised to "finish what we started" on a number of Obama-Biden priorities. "You have a right to know what I’ll do as president," he said in Cedar Rapids, Iowa, before saying he would roll back much of the 2017 tax cut, allow more people to buy into Medicare and make it easier to join a union.

Many other Democrats are running on more than that and saying, unlike Biden, that Trump's victory was not an anomaly so much as the culmination of decades of policy failure. That, and the slowed-down campaign style that Biden has adopted since 2016, are reasons why many Democrats believe they can cut through his "electability" pitch. Biden's Iowa crowds, entertained by bands that played covers of '60s and '70s pop rock songs, contained plenty of older voters who always caucus but few of the younger voters who crowd into Sanders or Kamala Harris or Warren events.

But the other candidates aren't cutting through yet. In Dubuque, 81-year-old Norm Duvé was among several voters who said they had been impressed by Warren, who had campaigned in Dubuque one month earlier, but were too nervous at the concept of a candidate who was a woman and lesser known than Biden challenging Trump.

"I don't think they're strong enough to carry it for themselves," Duvé said, before hearing Biden speak. "I'd like it if Biden ran with one of the good women."

READING LIST

"Asylum changes show Trump’s 2020 focus will again be on the border, presenting tough choices for Democrats," by Sean Sullivan, Josh Dawsey, and Matt Viser

Democrats have moved left on immigration since 2016, with the only political downside coming from attacks on "sanctuary cities" in red states. But the administration's constant focus on a border crisis is testing their resolve.

"Kamala Harris's questioning of Barr delivers a punch after an uneven stretch," by Chelsea Janes

The senator from California's team has speculated that her image as a prosecutor will help win Democrats who are imagining how candidates would stack up against Trump in debates. Harris's concise questioning this week reminded people of why they think that.

"Iowa voters flock to Joe Biden, but out of practicality, not passion," by Evan Halper

The crowd of Iowans saying they're for Joe because he's electable is really hard to miss.

"As Democrats prep for another health-care election, Trump gives them a big assist," by Paul Waldman

This opinion piece looks at how Democrats stop from time to time and marvel at how the administration is setting up a high-stakes health-care fight in June 2020, right before the conventions.

DEMS IN DISARRAY

To understand how Bernie Sanders might attack Joe Biden, it’s worth revisiting a moment from one of the senator from Vermont’s final debates with Hillary Clinton. In February 2016, the former secretary of state had told a debate audience in New Hampshire that her career had gotten bipartisan praise.

“I was very flattered when Henry Kissinger said I ran the State Department better than anybody had run it in a long time,” Clinton said.

One week later, on a debate stage in Milwaukee, Sanders unloaded on Clinton’s mention of Kissinger. “I find it rather amazing, because I happen to believe that Henry Kissinger was one of the most destructive secretaries of state in the modern history of this country,” Sanders said. “I am proud to say that Henry Kissinger is not my friend. I will not take advice from Henry Kissinger.”

Sanders went on to smash Clinton in Wisconsin’s primary, winning outright by 14 points and winning self-described “liberals” by 19 points, according to exit polls. And he has hinted that the same playbook will be useful in 2020; both the senator and his cheering section on the left see possibilities in Biden's habit of praising the character of Republicans and emphasizing how he signed on to bipartisan bills.

The latest example, tweeted Thursday by the Young Turks reporter Emma Vigeland, was a 2015 clip of Biden musing about how well he got along with his predecessor. “I actually like Dick Cheney, for real," Biden said, in a Minnesota forum with Walter Mondale. "I get on with him. I think he’s a decent man.”

That clip joined the growing archive of Biden praise for Republicans. “You were a hell of a governor,” Biden told Jeb Bush shortly before announcing his (Biden's) own campaign. "One of the finest guys I've ever worked with," Biden said last year of Rep. Fred Upton (R-Mich.), who helped resuscitate the (eventually doomed) effort to repeal the Affordable Care Act.

But the most dramatic clips of Biden being friendly with Republicans came later that year, when Biden spoke at the National Constitution Center to help give George W. Bush a medal. "As President Bush was my opposition as the chairman of the Foreign Relations Committee, he was never my enemy," Biden said. “I always respected the president.” Protesters repeatedly rose to heckle Biden and Bush before being removed from the room.

There's no starker rhetorical difference between Biden and Sanders than the former vice president's praise for the other side. Sanders is incredibly comfortable on the attack; Biden has limits. One of Biden's verbal tics is a discomfort with attacking a group of political enemies; when his crowds begin to boo, he tends to say that the people he’s criticizing are not all bad. In Dubuque this week, when Biden started to say that “CEOs, bankers and hedge fund managers didn’t build America,” he heard some jeers, then added that not everyone he was talking about were "bad people."

The Sanders and Biden theories of 2020 are completely at odds: One believes in giving voters a clear break with the "establishment" and a chance for war against it, while one asks audiences to go with him toward a less unruly and divisive politics. Sanders's surrogates and allies are on the warpath about Biden's get-along pitch; Sanders could join them there.

POLL WATCH

New Hampshire Democratic primary (Suffolk, 429 New Hampshire Democrats)

Undecided - 27%
Joe Biden - 20%
Bernie Sanders - 12%
Pete Buttigieg - 12%
Elizabeth Warren - 8%
Kamala Harris - 6%
Beto O'Rourke - 3%
Cory Booker - 3%
Tulsi Gabbard - 1%
Andrew Yang - 1%
John Delaney - 1%
Kirsten Gillibrand - 1%

A few national polls that showed Biden far ahead of the field reshaped the narrative about the Democratic race — was a Biden rout possible? The newest poll of New Hampshire cuts against that. It shows a contest that remains completely unsettled, with Bernie Sanders retaining about 1 in 5 of his 2016 voters and Biden operating at the sort of level that will encourage the second- and third-tier candidates to think that they could pass him. Biden, remember, has never gotten to the New Hampshire primary after two presidential campaigns.

What is your primary reason for not choosing Elizabeth Warren? (Suffolk, 393 New Hampshire Democrats)

She can't beat Trump - 18%
She doesn't excite me - 11%
She seems angry - 10%
Too liberal - 9%
The Native American issue - 5%

This is one of the more interesting questions a pollster has asked, and it's especially relevant in a state Warren cannot afford to lose. No surprise: The controversy over her Native American heritage claims, now in its seventh year, informs Democrats who worry that she is not as electable as their other choices. One in five Warren skeptics see her in the more ordinary way that moderate voters view left-wing candidates: She is too angry and liberal, therefore swing voters will not support her.

FROM THE Q&A

Read the full transcript of my chat on The Post's site here

Q. Which candidates are relying most heavily on a good debate performance? Which candidates do you think are well suited to break out during the debates?

A: Every candidate except Joe Biden believes that the debates will reorganize the race. The nice thing they'll say is that their candidates, who have been tenderized by voter questions and TV interviewers, will get to show off their skills. The not-nice thing, which they don't say, is that Biden's "electability" armor will be tested when the 76-year old veep is contrasted with younger candidates.

Having seen every candidate on the trail by now (I'm only going to say that once so nobody gets tired of it), I think that the candidates who've gotten the most nimble with questions are Buttigieg, Warren, Klobuchar, and Castro. Warren, Castro and Harris have shown some skills that could aid in a "breakout" moment AND have been underrated either for lack of attention or for the inordinate attention paid to their worst moments. 

Another big question, un-answerable for now, is which candidate might use the debate to make a negative case against a front-runner. You might say: Well, Bernie Sanders and Elizabeth Warren have been attacking Joe Biden's voting record. True, but we don't know if the debate lottery will put all three of them on the same stage; there will be, at first, two debates over two nights.

IN THE STATES

Missouri. Republicans control every branch of government in the Show Me State, and they are using it to water down a voter-passed initiative that would take away a partisan role in redistricting. The newest addition: The party wants redistricting to be based on numbers of voters, not all residents of the state, a change that would cut out the immigrants counted when states make their maps.

North Carolina. On Tuesday, voters in the state's 3rd Congressional District set up a race that Republicans are in a good position to win. Greg Murphy, a doctor and state legislator, will face a runoff against Joan Perry, a doctor and antiabortion activist who said she was spurred to run after Democrats introduced bills to loosen laws restricting late-term medical abortion. National Democrats had wanted Army veteran Richard Bew to win their primary; the nomination went instead to Allen Thomas, the former mayor of the city of Greenville. While the DCCC immediately attacked the GOP's "extreme" choices, they'd hoped for weaker candidates to make it to the GOP's runoff. Also noteworthy: Club for Growth-endorsed candidate Celeste Cairns ran a weak ninth out of 17 Republicans, and two candidates who had run advertisements contrasting themselves with Rep. Alexandria Ocasio-Cortez (D-N.Y.) lost badly.

2020

Michael Bennet. The senator from Colorado became the 21st Democratic candidate for president, writing in a Medium post that unlike some candidates, he does not dream of total Democratic control of government. "Even if all these policies had been wise, the one-party course would still be wrong. Sound, stable government can’t be a perpetual game of shirts and skins."

Kamala Harris. She's spending two days in southeast Michigan, a state that did not get much early attention in previous Democratic primary cycles.

Amy Klobuchar. She's heading to Michigan for the first time; she has previously campaigned in Wisconsin

Joe Biden. He's returning to South Carolina, the early primary state where he has polled the strongest, on Saturday and Sunday.

Bernie Sanders. He's back in Iowa this weekend for four events, and he's continuing to take questions at some of them, something Biden has not yet done.

Kirsten Gillibrand. She announced a Clean Elections Plan that would hand out "democracy dollars," money earmarked to help candidates in a publicly financed election system.

Beto O'Rourke. He's heading back to Iowa for six stops in two days. Something to watch: whether the younger candidates start to emphasize how much they're doing in front of voters, compared with Biden.

Larry Hogan. A super PAC created to support the Maryland governor, the Change Maryland Action PAC, has been soliciting donations again and raising eyebrows. (Hogan wants to cut into the Democrats' legislative majority in 2020, but he is term-limited and can't run again in 2022.)

WHAT I'M WATCHING

Caucus? What caucus? On Wednesday, Kansas Democrats released their new delegate selection plan for 2020, with a major change: a "party-run primary" replacing the traditional caucuses. On Thursday, Alaska Democrats did the same thing, exploring whether they could assign their 2020 delegates through a higher-turnout election.

No other change to Democratic primary rules, not even the de-powering of superdelegates, could have such potent effects on who wins the nomination. In the 2016 contest, 14 states bound their delegates to the results of caucuses, and Bernie Sanders won 12 of them. If every state party's new rules get adopted ahead of 2020, there will be just three real caucus states: Nevada, Iowa and Wyoming.

In the 28-year history of superdelegates, their presence never was enough to shift a party's nomination from one candidate to another. The same can't be said of caucuses. In 2008, Barack Obama only narrowly won more delegates at stake in primaries and caucuses than Hillary Clinton did; he edged her by 98 out of 3,385 delegates. In doing so, he out-organized her campaign in caucus states, picking up a few dozen more than he might have in all-day primaries. In Nebraska, for example, Obama smashed Clinton by 36 points in the caucuses, netting eight delegates over her. In the nonbinding primary, Obama won by just three points, a margin that would have netted him only one delegate over Clinton.

COUNTDOWN

... six days until Amy Klobuchar's town hall on Fox News
... 19 days until Pete Buttigieg's town hall on Fox News
... 31 days until Kirsten Gillibrand's town hall on Fox News