In this special debate day edition: The questions everyone is asking; the candidates left outside the hall; and the polls that explain why everyone not named "Elizabeth Warren” is worried. Expect another edition with post-debate analysis in your inbox tomorrow.

A broken hotel HVAC makes a very good alarm clock, and this is The Trailer.

COLUMBUS, Ohio — In the time between the third Democratic debate in Houston and the fourth Democratic debate tonight, the House began considering impeachment, Bernie Sanders began recuperating from a heart attack and Elizabeth Warren began to top the polls in Iowa. The president's reelection campaign went on the air against Joe Biden — who was facing more and more questions from Democrats who had considered him their most electable candidate.

There will be 12 candidates onstage, but expectations are highest for Biden, Warren and Sanders. The former vice president, who began his campaign by warning against a “circular firing squad,” is increasingly ready to portray Sen. Warren of Massachusetts as a weak candidate. “We’re not electing a planner,” he said last week in New Hampshire, a remark that wasn't in his prepared speech.

Warren, who has chipped away at Democratic worries about her electability, took more time off than usual before this debate: She has prepped for attacks on everything from Medicare-for-all to her corporate law work to whether she can be trusted to tell her life story. Sen. Sanders (I-Vt.), who delivered three strong debate performances in a row, is facing his lowest expectations ever, thanks to the health scare and sagging poll numbers. And nine candidates will walk behind their microphones in a markedly weaker position than Sanders.

Does the impeachment fight change anything? Three weeks ago, Democrats expected the start of the impeachment inquiry to freeze the presidential primary in place, crowding out candidates who hadn't commanded attention yet and giving center stage to Biden. That's exactly what's happened. Polling has found that Democrats even view Biden a bit more favorably because they believe the president made a false attack on his family. Polling has also found Warren, the first candidate to call for impeachment after the release of the Mueller report, rising and becoming Biden's closest competitor. 

Leading up to tonight, no Democrat has really shaken up that dynamic. When asked about the story and whether it was ethical for Biden's son Hunter to take a lucrative job with a Ukrainian energy company, every Democrat has swatted the question away. Sen. Kamala Harris (D-Calif.) puts it succinctly: “Leave Joe Biden alone.” Other candidates say they won't “play that game” or that President Trump is trying to “distract” them. No candidate has engaged with the substance of Republicans' “Quid Pro Joe” attack, which actually allowed Biden, on Sunday, to beat them on introducing a specific anti-nepotism ethics policy.

“No one in my family will have an office in the White House, will sit in a meeting as if they’re a Cabinet member, will in fact have any business relationship with anyone that relates to a foreign corporation,” Biden said, going after the president for giving political and policy work to his daughter, his adult sons and his son-in-law.

With mixed success, Biden has tried to turn the story into one of the president trying to disqualify his strongest opponent. It's in no other Democrat's interest to let that story line sink in. It's also not in their interest to side with the president against Biden. Any Democrat who uses the issue to raise questions about Biden's electability will be making news.

How much time do moderators and candidates spend on Medicare-for-all? A noticeable fatigue has set in with Democratic campaigns about the focus on Medicare-for-all — not the concept, but the specific legislation sponsored by Sanders. It doesn't have the votes to pass. Even some co-sponsors consider it more of a goal, or framework, than a 2021 agenda item. But over the first three debates, more time was spent discussing the intricacies of Sanders's bill than on any other single issue.

“They continue to ask the same questions,” said former HUD secretary Julián Castro earlier this month, grumbling about the moderators' Medicare-for-all focus.

Moderators, obviously, don't need to concern themselves with what the candidates don't want asked. Warren, who as Sanders has fallen back became the main target of Medicare-for-all attacks, has engaged in a long Road Runner-and-Wile E. Coyote game with reporters who keep trying to get her to say whether she'd raise “middle-class taxes” to create universal health care.

“Costs are going to go up for the wealthiest Americans, for big corporations, and hard-working middle-class families are going to see their costs going down,” Warren said in the interview with Stephen Colbert that perked Democrats (and some reporters) up to the stump-the-candidate possibilities of the question.

For Warren's opponents, the dream scenario is simple: a fusillade of private insurance/tax questions that force her either to recycle her talking points or knock her off balance. For Sanders, it's more complicated: Warren is the only co-sponsor of Medicare-for-all in the race who hasn't backed down from it in some way, but it's his legislation, and he knows that one reason some Democrats prefer Warren to him because they don't expect her to stake her presidency on it. 

Does anyone go after Warren's integrity? The Massachusetts senator is the one candidate who's entered every debate in a stronger position than the previous one. It's not because rivals refused to attack her. The second debates, in Detroit, began with an hour of back-and-forth between lower-polling centrist candidates and the Warren-Sanders duo about, yes, Medicare-for-all. The third debates began with moderators saying that Warren and Sanders wanted to “replace Obamacare” and Biden didn't want to “scrap it,” exactly the framing that Biden uses on the trail.

But over nearly nine hours of debates, no one has challenged Warren on her past claims of Native American heritage. No one has attacked her legal advice for corporations. No one has pointed out that she was a Republican until Bill Clinton's second term, though Warren’s allies consider that a general election boost.

Warren's campaign has prepped for all of this, and more, including her votes for Trump's first two National Defense Authorization Acts. (That hasn't been a flash point between candidates, but it's been a theme of social media attacks on Warren, contrasting her with Sanders and Hawaii Rep. Tulsi Gabbard, who have opposed every Trump-era NDAA.) Gabbard, who used the second debate to attack Harris's criminal justice record, looms as a threat, largely because she's the only Democrat who's actively celebrated her ability to go negative. 

Does any Beto O'Rourke/Pete Buttigieg animus spill onto the stage? The former Texas congressman has not concealed his contempt for the kind of campaign Buttigieg is running. O'Rourke cultivates small donors; Buttigieg holds high-dollar fundraisers (while also growing his small donor base). O'Rourke makes passionate stands on uncomfortable issues, like gun safety; Buttigieg is a picture of Zen, taking popular positions that O'Rourke (and not only O'Rourke) consider hatched from a polling farm.

“To those who are worried about the polls and want to triangulate or talk to the consultants or listen to the focus groups — and I’m thinking about Mayor Pete on this one, who I think probably wants to get to the right place but is afraid of doing the right thing right now — to those who need a weatherman, let me tell you that in this country, mandatory buybacks are supported by a majority of Americans,” O'Rourke told Politico in the debate run-up.

Buttigieg hasn't disguised his own irritation with O'Rourke. He told CNN on Sunday that the Texan had bungled an answer at the network's LGBTQ town hall on religious liberty, specifically on whether religious organizations would lose tax exemption if they discriminated: “I'm not sure he understood the implications of what he was saying.”

Is there any upside now to going negative? There hasn’t been so far. Gabbard, who’s leaned into her reputation as the knife-fighter who “destroyed” Harris, has remained in the low single digits. The bounce from Harris’s own first debate showdown with Biden has faded. Castro’s numbers, both his personal favorable and his strength in trial heats, have declined to near-zero since he audaciously told Biden, last month, that he had forgotten the details of his own health-care plan. Democrats simply don’t reward candidates if they come off “mean.”

“There’s remarkable situational awareness that we must defeat Donald Trump,” DNC Chairman Tom Perez said Tuesday after a party event near the debate. “If we come out of the primary cycle limping, instead of sprinting, it will make it harder.”

What is Tom Steyer doing here? Democrats really don't know what to make of the billionaire who entered the race in June after saying he wouldn't. He has taken credit for starting the ball rolling on impeachment and has lumped every other candidate together as a politician who does not have his experience in “making change happen.” (That's the tag in his ads, which emphasize everything from his passage of ballot measures in California to his creation of a lending program for minority businesses.)

Strategists at several campaigns said they would probably ignore Steyer, unless he unexpectedly went hard negative. They simply see him as more of a nuisance than a strategic threat: a wealthy white donor who has spent eight figures of his own money to poll in the low single digits. And he’s never, ever participated in a debate before, something his campaign emphasized this week.

“Tom’s not a Washington politician,” Steyer’s campaign manager Heather Hargreaves said in a pre-debate email to reporters. “He’ll be up against 11 other candidates who’ve done this 2-3 times this year and throughout their whole careers.”

There were already plenty of land mines waiting for candidates if they decided to come out slashing tonight. Steyer’s campaign bought another batch of them.

READING LIST

“The transformation of Elizabeth Warren,” by Holly Bailey

The Democrat's little-known Houston years, when she developed her teaching style and had a brush with sexual harassment.

“Missing from Elizabeth Warren’s 2020 surge: Democratic endorsements,” by Jonathan Martin

Why a surging candidate hasn't persuaded governors or many Senate colleagues to endorse her.

“Bernie Sanders’s plan would force country’s largest corporations to share profits with workers,” by Chelsea Janes and Jeff Stein

A pre-debate plan to reform capitalism that goes even further than Warren's.

“Hunter Biden says role with Ukraine firm was 'poor judgment' but not 'improper,' ” by Cleve R. Wootson Jr. 

The son at the center of a national drama speaks on camera for the first time.

IMPEACHMENT WATCH

The latest reporting and analysis on the impeachment inquiry

AD WATCH

Pete Buttigieg, “Makes More Sense.” This is the latest in a series of contrast spots on Medicare-for-all; Buttigieg has run one, Sen. Michael Bennet of Colorado has run several. It's designed for digital audiences, not TV, so it takes a bit more time than normal getting to its point. And how it does so is telling: by using the voices of TV commentators and reporters making the case against the left's signature health insurance proposal, saying “union workers are a little skeptical” and “there are 160 million Americans who get their insurance from their employer.” That takes the onus off Buttigieg, important when Democratic voters haven't been rewarding candidate-on-candidate attacks.

Joe Sestak, “United.” One of the last Democrats to enter the race, former congressman Sestak has tried to break through with constant in-person campaigning, then attract media attention. The media attention has been sparse, so Sestak is going on the air earlier than expected with the message he used in every Pennsylvania campaign: He spent a career in the military and was moved to run for office after his daughter beat brain cancer. (Some of this, and some of the same file footage, appears in the ads from Sestak's 2016 race for U.S. Senate.)

POLL WATCH

Which candidate has the best chance of winning the general election? (Quinnipiac, 505 likely Democratic voters)

Joe Biden — 48% (-1)
Elizabeth Warren — 21% ( 12)
Bernie Sanders — 7% (-5)
Pete Buttigieg — 2% ( 1)
Kamala Harris — 1% (-5)
Beto O'Rourke — 1% (-1)

Democrats have wrestled with the “electability” question all year. The only difference in what they're arguing about is that more of them have begun to take Warren seriously. In April, when Biden joined the race, 56 percent of Democrats considered him to be their strongest general election candidate. That number plunged after his first, weak debate performance, but he still led the field on electability, at 42 percent, and he's stayed close to a majority on that question since. It's Warren who's really moved since April, when just 3 percent of Democrats considered her their safest general election bet. What had been a 53-point deficit to Biden has shrunk to 27 points.

That's still a big gap, and a consistent one. In every demographic, Warren does slightly worse on electability than she does in a head-to-head with Biden. Among all white Democrats, she leads by 14 points; white Democrats say Biden is more electable by 21 points. Black voters view Biden as more electable than Warren by 47 points, while voters under 35 — Biden's worst age demographic — see him as more electable by 12 points.

Should there be a government health insurance plan for everyone? (CBS News/YouGov, 1,292)

Yes — 66%
No — 30%

If Democrats are cursed to debate Medicare-for-all at length every few weeks, this is among the reasons why: The concept of national health insurance has taken off since Republicans botched their 2017 drive to repeal the Affordable Care Act. When pressured, Sanders frequently cites the high poll numbers for something describable as “Medicare-for-all” as proof that he gets it and the media does not. Asked if they’re happy with their insurance, 85 percent of Medicare recipients say they are; the number is 13 points lower for people with private insurance.

But that’s the rub, and it’s why there will probably be another health insurance spat tonight. By a 27-point margin, voters prefer a public health-care option that would compete with private plans over a total replacement of the for-profit insurance system. Among Democrats, it’s a popular idea — 65 percent say the Affordable Care Act did not go “far enough” in providing insurance. The intra-Democratic argument is whether they should run on something that most of their voters like or not.

2020

The largest Democratic primary debate in the history of the universe will not, of course, bring every Democratic candidate onstage. Six active candidates did not qualify for the debate — one (Marianne Williamson) who met the 130,000 donor standard but fell short on the polling standard, and five who hit neither mark.

Michael Bennet. He's campaigning in Iowa and holding a town hall during the debate; tomorrow he's in New Hampshire, delivering a speech on “a plan for an economy that rewards hard work.”

Steve Bullock. He's in Helena, Mont., with no campaign plans until later in the week. “We may well be, like two-thirds of Iowans, not even watching,” Bullock told reporters Sunday before an appearance at a labor forum.

Tim Ryan. He had been rallying with striking members of the UAW but is taking a day off the trail as his mother undergoes surgery.

Marianne Williamson. She's speaking in Encinitas, Calif., during the debate, with remarks on “the spirit of America.”

Joe Sestak. He's continuing his walk through New Hampshire, with occasional stops to talk to local Democrats.

*Wayne Messam, a Florida mayor who got a little national attention when he launched his presidential campaign, is often included in long lists of the Democratic candidates. But he lost most of his staff months ago, has not held a public campaign event since July and has ignored invitations to “cattle call” party events. He's not really competing for the nomination.

COUNTDOWN

... 17 days until the Iowa Liberty and Justice Celebration
... 21 days until state and legislative elections in Kentucky, Missisippi, New Jersey and Virginia
... 29 days until the cutoff for the fifth Democratic debate
... 32 days until Louisiana's runoff elections
... 36 days until the fifth Democratic debate