Former vice president Joe Biden speaks to fellow Democratic presidential hopeful Rep. Tim Ryan (Ohio) on Friday at the Wing Ding in Clear Lake. Some Democrats are concerned about Biden’s ability to take on President Trump in a general election, should he become the nominee. (Melina Mara/The Washington Post)

DES MOINES — As Democrats descend on Iowa to kick off a six-month sprint to the first primary vote, party activists are increasingly anxious that former vice president Joe Biden, the consistent polling leader, has not disposed of persistent questions about whether he is well-equipped to take on President Trump.

Adding to the Democrats’ nervousness is that a clear alternative has yet to emerge. Sen. Elizabeth Warren (Mass.) is rising in the polls and has a high-quality campaign organization, but doubts linger in some quarters about the appeal of her left-leaning policies in a general election. Sens. Kamala D. Harris (Calif.) and Bernie Sanders (I-Vt.) are struggling to maintain momentum, while pressure is growing from frustrated voters for many of the weaker candidates to drop out.

That shaky landscape is prolonging the uncertainty in a nominating contest that Democrats describe as the most important of their lifetimes, and it puts the party in the unusual situation of having a leader who draws on a deep well of affection but also gives a lot of people in the party jitters.

Democratic presidential hopefuls made a stop at the Iowa State Fair, giving speeches, eating fried foods and drawing large crowds. (Video: The Washington Post, Photo: Salwan Georges/The Washington Post)

“Joe Biden can resonate with the working-class voters that Trump fooled in the last go-round. And that’s what we need: He’s close to the middle. He’s a known quantity. He appeals to middle-class voters,” said Alan Feirer, the party chairman in Madison County.

“But boy, he’s old,” Feirer added. “That shouldn’t be a problem, and you don’t like to say it, but he isn’t as compelling verbally. . . . There is starting to be a real fear that he cannot hold his own in the debate against Donald Trump.”

Tracy Freese, the county chairwoman in Grundy County, said she, like many, has conflicted emotions about Biden.

Iowa is awash in candidates, but don’t expect clarity until the very end

“I wish he’d get his mojo back. I know he has it; I just haven’t seen it,” Freese said. She longs for the Biden who took on Paul D. Ryan in the 2012 vice presidential debate. “Where did that guy go?” she said. “I’m not seeing him right now.”

At the same time, Freese understands, intellectually at least, the argument that Biden may have the best chance of attracting GOP voters. “I’m done falling in love. I’m falling in line,” she said. “I do struggle with it, but I just want Republicans to be able to feel comfortable and vote for him.”

Those crosscurrents are converging in Iowa and will play out here in the coming months. After a somewhat turbulent, shapeless stretch, the primary race is beginning to focus sharply on this state, where the caucuses on Feb. 3 will be Democrats’ first opportunity to actually vote in this extended primary contest.

This weekend, the Democratic candidates have come together for three big Iowa events — the “Wing Ding” dinner in Clear Lake, an increasingly important party gathering; a forum on gun control in the aftermath of the recent mass shootings in El Paso and Dayton, Ohio; and the Iowa State Fair, a colorful spectacle that features endless fried food on sticks and a famous “soapbox” where candidates speak amid hay bales.

Unlike many previous races, every presidential candidate is taking Iowa seriously this time, including those who earlier this year were paying it scant attention. Harris is airing an early television ad here and taking a bus tour through the state, and on Saturday she announced the endorsement of Bob and Sue Dvorsky, prominent Democratic activists who were courted by many in the field. Biden, for his part, is mounting one of his longest campaign swings here, and has recently gone on a hiring blitz to build one of the largest campaign staffs.

Many Democratic voters here say they have narrowed the field to a half-dozen possible choices. And much of the focus is on the lingering concerns about Biden.

The problems have cropped up as recently as his current Iowa swing. Most of the missteps are minor, but they risk adding up to an overall picture of a politician whose sharpest days are behind him — an image seized by Trump at every opportunity, and one the president would probably mention unceasingly should Biden be the nominee.

On Saturday, he said he met with Parkland students while he was vice president, even though the Florida shooting took place a year after he left office.

Democratic presidential candidate Joe Biden corrected himself in Des Moines on Aug. 8 after he compared children living in poverty to white children. (Video: Reuters)

In his speech Thursday at the state fair, Biden bungled a line and said, “We choose truth over facts!” He initially referred to former British prime minister Theresa May as one of her predecessors, Margaret Thatcher. And speaking before a Latino and Asian group, he argued for challenging students in underserved areas — but briefly appeared to conflate whiteness and wealth.

“We have this notion that somehow if you’re poor, you cannot do it,” he said. “Poor kids are just as bright and just as talented as white kids.”

He caught himself and quickly added, “Wealthy kids. Black kids, Asian kids. No, I really mean it, but think how we think about it.”

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Some of Biden’s Democratic rivals seized on the stumble. Rep. Tim Ryan (D-Ohio), who was born the year Biden arrived in the Senate, hoped the gaffes inspired voters to take a second or third look at younger candidates.

“This is such an important election, and we’ve all got to be at our best,” Ryan said. “We all can’t make mistakes because with the right-wing noise machine, they take something like that, and they put up a false equivalency, making him and Trump sound like they’re the same.”

Trump indeed took a shot at Biden after the flub, speaking to reporters at the White House on Friday. “Joe Biden is not playing with a full deck,” the president said. “This is not somebody you can have as your president.”

Such episodes give some Democrats pause. As Arlene Davis, 67, a retired schoolteacher from Indianola, waited to hear Biden speak the other night, she panned his candidacy so far, especially his debate performances.

“I was extremely disappointed. I expect more of him. He was uninspired,” she said. “He’s trying to ride Obama’s coattails instead of blazing his own path to distinguish himself from others. Gee, it was nice he was vice president. However, he is not vice president now, and if he wants to stand out, he has to do it soon, on his own two feet.” Davis added: “I want to know what he thinks, not what he did with Obama. That’s why I’m here.”

But Biden’s appearance that evening evidently did not convince her: Halfway through, she took out her phone and began playing a card game.

Nearly all the two dozen Democratic candidates have descended on the state over the past several days, at the culmination of a week when two mass shootings fueled a wrenching national debate over highly divisive topics: gun control, immigration and Trump himself.

Yet there is a sense in Iowa that no Democrat is turning in a slam-dunk performance, at least yet. “No candidate seems to be catching total fire, the way that some candidates have in the past,” Feirer said. “Every candidate has a serious asset that they bring to the race and also at least one liability. There’s no perfect candidate.”

Sean Bagniewski, chairman of the Polk County Democrats, added, “It’s weird that it’s still this chaotic and this open at this point still.”

It’s an uncertainty that collides with the passionate, almost desperate desire among rank-and-file Democrats to start taking the fight to Trump.

In surveying nearly half of the state’s 99 Democratic county chairs this week, there was widespread agreement that Warren has the most formidable organization. Her staffers have been showing up for months in rural and urban counties alike, holding meetings in small diners, helping at community events and running in local 5K races. Other campaigns are starting to make inroads, but they are months behind.

Presidential candidate Sen. Elizabeth Warren (D-Mass.) said that by 2020, President Trump "may not even be president. He may not even be a free person." (Video: Reuters)

There is also a deep desire for the field to narrow, and soon. Many Democrats say they are eager for a younger nominee — which suggests doubts about Biden and Sanders — and party leaders say the enthusiasm for Biden in their counties is, at best, lukewarm.

Biden believes Iowa is crucial for him — he referred to it the other day as having “the keys to the kingdom” — but it also presents some of his greatest challenges. The state lacks many of the black voters who have provided the bulwark of his support nationally, and his more moderate views may be unsettling for the liberal Democrats who reliably attend the caucuses.

For now, he is projecting a brash confidence mixed with a recognition that his current position atop the polls is no guarantee. “You know, it’s way early on,” he said at one recent Iowa campaign stop. “I know the polls had me ahead by 10 or 12 points to the next person, but it’s early. It’s real early.”

Two minutes later, he was asked whether he can electrify people in a way that’s needed to win. “Look at the polls,” he said. “So far, so good. So, I do it by being me.”

As Biden roamed through the grounds at the Iowa State Fair, a reporter asked if he thought he had earned any votes that day, and he replied, “What do you think? Anybody draw a bigger crowd? Don’t be a wiseguy.” (Biden was one of two speakers that day, coming after Montana Gov. Steve Bullock, whose crowd was a bit smaller.)

When asked if he felt like the front-runner, he let out a big laugh. “Is that target still on my back?” he asked.

Warren, meanwhile, has been steadily planting a far-reaching network and creeping up in the polls. Nearly every Iowa county chairman said that for months, they have seen her campaign tending to local party committees and carefully identifying supporters.

Bagniewski, the Polk County chairman, reached out in July to all of the presidential campaigns, seeking volunteers who could help run the caucuses in 40 precincts. Within 48 hours, Warren’s campaign had supplied volunteers to fill half the needed positions; no other campaign has filled even one.

“They have so many caucus-night volunteers that in those precincts they have two people and can give us one. That’s nuts,” Bagniewski said. “Some other campaigns tried to give us names of leads, but nobody else has been able to do that at all. Not even one or two. It really is exceptional.

As they struggle to rally around a single nominee, Iowa Democrats are worried that the unprecedentedly large field is damaging their chances of defeating Trump. Voters say they are inundated with phone calls and emails to the point of being turned off.

“I have started ignoring my email and phone calls. It is too much. There are too many running,” said William Baresel, Democratic chairman in Floyd County.

Some of the candidates appear to be emulating John F. Kerry’s 2004 primary campaign in Iowa. Kerry’s operation faltered early on but resurrected, and he was positioned to reap the benefits when the front-runner struggled, becoming the eventual nominee.

But there is another, even more auspicious model. Barack Obama in 2008 slowly built a network, religiously identified supporters and then turned them out on caucus night. That victory gave him momentum in the nominating contest that he never relinquished.

Democrats urgently want another candidate who can capture that magic.

“One reason many of us . . . aren’t ready to put signs in our yard is that we recall the time early in 2008 when a young woman came to our county and stumped for her husband,” said Marjie Foster, chair of Decatur County Democrats. “No one had ever heard of her or her husband at the time. But a year later we were inaugurating him, and she was our first lady.”