Fort Dodge, Iowa (CNN) Joe Biden 's fundraising slowed so much that allies launched a super PAC . He's slipped in the polls enough to drop from Democratic 2020 front-runner into what's now a three-way top tier. And he's faced relentless personal attacks from President Donald Trump.

But the former vice president has one asset other Democrats don't: Polls, both nationwide and in the early states, continue to show that aplurality of voters continue to say they see him as the party's most electable candidate.Biden is seen by 42% of likely Democratic voters nationally as the most electable candidate compared to Warren's 20%, a Quinnipiac University poll released last week found -- even as that poll showed Warren with a seven-point lead over Biden.

That view has left Biden with a core group of supporters that is so far proving stickier than many Democratic activists and rival campaigns expected -- unmoved by his occasional gaffes and the backlash he has at times faced on the Twittersphere.

Over one of the most important weekends in the lead-up to 2020, Biden's challenge is to make sure voters here in the Hawkeye State. where he is currently in the middle of a four-day swing, continue to see him that way -- and convince them it's the most important quality in choosing their Democratic nominee.

Now, three months out from the Iowa caucuses, the race is shifting into a critical stretch that starts Friday night in Des Moines, when 14 candidates attend the Iowa Democratic Party's Liberty and Justice Celebration -- with a crowd of more than 12,000 expected to fill Wells Fargo Arena.

It's a marquee event that has offered trailing candidates their breakout moments in previous elections. Then called the Jefferson-Jackson Dinner, it helped catapult then-Sen. Barack Obama past Hillary Clinton in the run-up to the 2008 Iowa Democratic caucuses.

In recent months, as Massachusetts Sen. Elizabeth Warren caught up with Biden in Iowa polls, his aides have acknowledged he could lose the state -- but they insist he could withstand the loss. Aides point out he is currently in a dominant position in South Carolina, a state where black voters make up a much larger share of the Democratic electorate, and his campaign believes he would then rack up delegates on Super Tuesday.

Still, with a campaign built on his electability, Biden could struggle after a poorer-than-expected performance.

On Thursday in Fort Dodge, Biden told reporters, "I feel good about where we are."

"We're doing fine. We feel good," he said. "I think we have one of the best organizations in this state and around the country."

Thinking ahead to the general election

Biden's rallies are a jarring break from other leading Democrats' events. He doesn't draw the massive crowds that his rivals do -- and generally doesn't even book large venues. Those who are there, even when Biden campaigns on college campuses, tend to be older and whiter than the crowds other candidates are drawing. Attendees crowd the ropeline afterward for handshakes and selfies with Biden -- and that's where Biden, a skilled retail politician with a gift for making personal connections, is often at his best. But they don't linger for hours for pictures the way they do after Warren speaks.

Still, his events do offer a glimpse into a phenomenon of the 2020 Democratic presidential primary: Voters act as political pundits now, obsessed with gaming out their party's potential general election match-up with President Donald Trump.

Even in the early-voting states, voters with the power to shape the primary's narrative are viewing the race through a national lens. They routinely say they are judging candidates just as much by their television appearances and debate performances as their opportunities to meet and hear them in person.

It's partly how voters culled their lists of candidates to consider from the two dozen that entered the race. And it's a result of a Democratic electorate that polls show -- in 2020 much more than previous elections -- are focused on electability in choosing their nominee.

Other Democrats have their own cases to make around their electability: Vermont Sen. Bernie Sanders leans into his ability to turn out young voters and independents. Warren argues that voters of all stripes detest what she characterizes as a fundamentally corrupt system. Former Texas Rep. Beto O'Rourke insists he could win Texas and its 38 electoral votes -- all but guaranteeing Democratic victory.

But Biden's is the most straightforward. In his campaign's view, Biden's road to the White House is a simple formula: a net of 80,000 more votes against Trump in Wisconsin, Michigan and Pennsylvania. Anything after that would just pad his win.

Biden's television advertisements in Iowa have emphasized that point.

"We have to beat Donald Trump and all the polls agree Joe Biden is the strongest Democrat to do the job," a narrator said in his first spot to air in Iowa in August.

The concept of Biden's electability has frustrated his opponents, who see it as a self-fulfilling prophecy -- one that's overly influenced by white, moderate voters, and ignores the party's diversity and its potential to make gains elsewhere in 2020 -- and argue that voters would select a stronger general election nominee by backing the candidate who inspires them.

But at Biden's events in Iowa this week, attendees explained why they are backing Biden -- or at least considering it: Even if they align more closely with other candidates' policy views, they believe he can beat Trump, particularly among independents and moderate Republicans in the Midwest.

Mary Herring, a retired public school teacher and university professor from Maquoketa, said before a Biden event Wednesday that she's deciding between what she sees as the centrist candidates -- Biden, Minnesota Sen. Amy Klobuchar and South Bend, Indiana, Mayor Pete Buttigieg -- because she's looking for a Democrat who can win among moderates in the general election.

"I think it's the middle-of-the-road people who helped make the decision in 2016. And I just think they will appeal to a broader audience," she said. "I know that Trump had his core and Hillary had our core, but it's all the people in between that make the ultimate decision."

Biden's "got experience. He's got charisma. I see tonight the energy," said Helene Hill, a 69-year-old retiree from Dubuque.

"Joe is way above the others politically and in experience," she said.

Laura and Ray Orris, a Dubuque couple in their early 30s, said they were considering backing Biden, Warren or Buttigieg.

"I'm trying not to be an idealist and trying to be practical about it," Laura Orris said. "But at the same time, wanting what we want and wanting to fight for the policy that we want -- and so there's that balance that you have to strike with finding something practical."

Most of his supporters say their confidence in his electability hasn't been swayed by Trump's attacks on Biden and his son Hunter, which has included a barrage of digital ads attacking the former vice president.

Over and over, voters said they didn't think the Bidens had done anything wrong -- or if they did, it paled in comparison to the Trump family.

But some said they fear the attacks will damage Biden's chances of winning the general election.

"It doesn't affect the way I view him, but I know it's going to affect the way others view him," Ray Orris said. "And that's what worries me."

Biden's Iowa strategy

Biden aides argued that he is the strongest candidate among moderates, rural voters and older voters -- who reliably turn out for the caucuses in Iowa.

Jesse Harris, a senior Biden adviser in the state, said the campaign is emphasizing outreach to the people it already knows are backing Biden. That group is crucial to keep behind the former vice president due to Iowa Democrats' rules that supporters of candidates who don't reach 15% support during the first alignment at individual caucus sites have to back a candidate who did hit that threshold.

"People then start to look at who they think is electable, and then he grows his coalition that way, too," said state Sen. Jim Lykam, a Davenport Democrat who backs Biden.

Jackie Norris, the Biden-backing former chief of staff for Michelle Obama and current president of Goodwill of Central Iowa, said Biden "started behind, and I think they're willing to accept that they started behind," she said.

But Norris said Biden's campaign is on track now, and beginning to focus on identifying likely caucus-goers who could back Biden after their candidates fail to meet the state's 15% threshold and they're forced to back their second choices on caucus night.

"When you think about the pinpoint accuracy needed on the ground, it's, does your precinct captain know walking into that room who's for Bennett or who's for Bullock, and are they ready to go after them after the first alignment?" she said. "It's that level of detail that I think that the Biden folks are beginning to focus on, and I think that they're on schedule."

Another challenge facing Biden's campaign in Iowa, Norris said, is that he hasn't spent as much time in the state as other contenders.

A prime example came Thursday. Biden had held two rallies the day before in eastern Iowa. But instead of spending Thursday holding several more events, he left the state for a fundraiser in Columbus, Ohio. Biden was back in Iowa by late Thursday afternoon for a rally in Fort Dodge -- his only event in the state that day.

"It is very hard when you don't have the candidate to come in and catalyze a relationship. I think that's hard. I don't know if that's going to change. So you're always playing at a little bit of a disadvantage," Norris said.