CLEAR LAKE, Iowa — With fake palm trees and a huge American flag as a backdrop, Senator Elizabeth Warren skipped onstage, microphone in hand, and barreled through her proposal to help rural America. In parting, she flapped her arms in a lightning-quick dance as Dolly Parton’s “Nine to Five’’ played her off.

“We’ve had enough of an America where government works better and better for a thinner and thinner slice at the top — 2020 is our chance,’’ Warren said to the crowd with her trademark bouncy energy.

Right behind her, former vice president Joe Biden trod to the microphone, note cards in hand, and delivered a somber rejoinder, casting President Trump as an existential threat to a grieving and divided nation.

“Not a single thing can happen,’’ he said, “unless we defeat Donald Trump.’’

It was the end of a long string of candidate speeches Friday night at the Iowa Democratic Wing Ding, a marquee party fund-raiser that, along with the just-opened Iowa State Fair, essentially marks the beginning of the fall campaign season. It was also a rare ­almost-meeting between Biden, who consistently tops the polls among Democratic presidential candidates, and Warren, the ­ascendant liberal angling to knock him from his perch in this key state.

“The caucuses aren’t today, but if they were today, you’d have to think we saw the likely two top finishers back to back,’’ said Kurt Meyer, chair of the Tri-County Democrats.

Through two rounds of debates, Biden and Warren have yet to face each other directly. But the tableau this weekend shows how they are circling each other ever more closely, at a time when Democratic voters are increasingly agonizing over which candidate is best suited to beat Trump, rather than which more perfectly fits their own politics.

And that question appears to become even more urgent after a painful summer of mass shootings and deeply divisive statements from Trump.

“It’s Biden’s best strength that, right now, people perceive he’s most electable,’’ said Grant Woodard, an attorney in Des Moines and former Democratic operative. “With Warren, she needs to overcome that. She needs to convince people of that, and if she does, I think she’ll win here.’’

Interviews this weekend revealed some voters questioning the received wisdom about the safety of a Biden candidacy, as he commits gaffes and stumbles over some words, which could boost Warren or Senator Kamala Harris.

“I just have a little bit of a problem with Biden as the front-runner, if he can really do it,’’ said Joann Kinyon, as she took part in an Iowa fair political tradition: registering her choice of candidate by dropping a kernel of corn into a jar labeled with Warren’s name. “I think she can do the job.’’

A recent poll from Monmouth University showed Biden with 28 percent support in Iowa, and Warren at 19 — up from 7 percent in the organization’s last poll in April. Warren is frequently described as having the superior political operation here, but Biden’s shop is quickly bulking up.

The weekend braided two American traditions of spectacle and sorrow in sometimes jarring ways. There was the ritual parade of candidates through the fair, with voters pressing in as Harris flipped pork chops and Representative Tulsi Gabbard of Hawaii sought out a vegan corn dog.

Those timeless, carefree moments were a stark contrast to a kind of national mourning over the mass shootings in Texas and Ohio, which infused the days with moments of silence and fueled more resolve in Democrats to defeat Trump.

“We all need to think about them,’’ Iowa state Representative Sharon Steckman said of the shooting victims, “and get somebody in office who will do something about it.’’

Biden has held the lead in polls since he entered the race in April. But interviews with voters turned up doubts about his electability advantage.

“I love Joe Biden, but he seemed old and tired during the debates,’’ said Abdi Ahari, 50, a surgeon from Mason City, Iowa, as he lined up outside the Wing Ding. “Politicians have shelf lives, and he’s expired.’’

Here in Iowa, Biden flubbed some lines, as when he declared, “We choose truth over facts,’’ instead of “truth over lies,’’ or referred to the former British prime minister Theresa May as “Margaret Thatcher.’’ On Thursday, he declared, “Poor kids are just as bright and just as talented as white kids,’’ before correcting himself and adding “wealthy kids, black kids, and Asian kids.’’

David Axelrod, chief strategist for Barack Obama’s campaigns, said it is possible such incidents could change perceptions of Biden as a safe bet.

“If, through his behavior on the stump, [that] gives them cause for concern, then he’ll become a more risky candidate,’’ Axelrod said.

Some voters pointed to Warren and Harris as among the candidates who are better equipped to take on Trump, suggesting the pair’s commanding debate performances could be shifting the conventional thinking on electability.

If Trump were to debate Warren, said Steve Epperly, 74, “I think he would be wrestling a tiger there.’’

“She’s got all her ducks in a row. She knows how to express herself. She doesn’t have to get real wordy about it,’’ Epperly said, adding that Biden “kind of floats off once in a while.’’

Some voters at the Wing Ding were struck by the contrast between the 70-year-old Warren, with her high-energy policy treatises, and the 76-year-old Biden and his reflective reminder of the election’s stakes.

“He’s like, ‘words of wisdom.’ She’s like, ‘words of action,’’’ said Joyce Glover, 79, who traveled here from Wisconsin.

“He’s as old as we are. I know how tired you get at this age,’’ said her sister, Daisy McKinley, 76. She added Warren had displayed “so much more life and oomph.’’

Warren toured Iowa this week, talking up her plan on rural America and an ambitious proposal to cut gun deaths, which she rolled out Saturday. At the fair, she indulged another tradition, stepping onto a soapbox for her turn before the audience, to be greeted with calls of “big structural change’’ and “2 percent’’ — a reference to her proposed wealth tax.

“When you see a government that works great for the rich, those with money, works great for those with connection, isn’t working for much of anyone else, that is corruption pure and simple,’’ Warren said, as the crowd cheered.

To be sure, Iowa seems far from a two-person race. Harris scored a top endorsement from Sue Dvorsky, former chair of the state party, and her husband, Bob, a former state senator. Pete Buttigieg was greeted by adoring crowds and was tied with Warren for second in the corn-kernel poll through Saturday afternoon.

Many voters here were still weighing their options, with electability at the front of their minds. Sue Meyer, a Des Moines resident, watched Harris pass by in a crush of reporters, and said she was deeply torn between her, Warren, Minnesota Senator Amy Klobuchar, and, “as much as it pains me to say it, Joe Biden.’’

“We need a new voice,’’ Meyer said, but conceded, “he’s the safe choice.’’

Iowa still has the power to make a statement about a candidate’s electability. It catapulted Obama to the top of a crowded primary field in 2008. Bernie Sanders’ razor-thin loss to Hillary Clinton in 2016 presaged his endurance in a nomination fight that many observers had assumed would be over quickly.

“Iowa launched him in a way that was decisive,’’ said Axelrod, the Obama strategist. “So, you know, it can have that same impact for another candidate — perhaps her.’’

Jess Bidgood can be reached at Jess.Bidgood@globe.com. Follow her on Twitter @jessbidgood.