WAUKEE, Iowa — In person, two leading Democratic presidential candidates are increasingly drawing contrasts with their chief rivals as they make their final pitches to Iowa voters ahead of Monday's caucuses. But on the airwaves, it’s all about President Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE.

Former Vice President Joe Biden Joe BidenBiden leads Trump by 36 points nationally among Latinos: poll GOP set to release controversial Biden report Can Donald Trump maintain new momentum until this November? MORE took aim on Thursday at Sen. Bernie Sanders Bernie SandersNYT editorial board remembers Ginsburg: She 'will forever have two legacies' Two GOP governors urge Republicans to hold off on Supreme Court nominee Sanders knocks McConnell: He's going against Ginsburg's 'dying wishes' MORE (I-Vt.), who has led several recent polls, for Sanders’s past votes against gun control measures like the Brady Bill and over the fact that Sanders is not a member of the Democratic Party.

Hours earlier, former South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegBipartisan praise pours in after Ginsburg's death Bogeymen of the far left deserve a place in any Biden administration Overnight Defense: Woodward book causes new firestorm | Book says Trump lashed out at generals, told Woodward about secret weapons system | US withdrawing thousands of troops from Iraq MORE challenged Biden’s claim that he is the most electable candidate in the field.

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"The less 2020 looks like 2016, the better,” Buttigieg said Thursday in Ankeny. “I’ve seen Vice President Biden making the case that we cannot afford to take a risk on a new person right now. I would argue that at a time like this, what we can't afford to take the risk on is falling back on the familiar, because history has shown us we've got to look to the future in order to win."

Buttigieg also called out Sanders, saying he was "offering an approach that tells folks who are not sure about going all the way to one side that they don't fit."

"I think this is a moment to build on the majority that now exists, even more than what President Obama had to work with 10 years ago,” he said.

Misty Rebik, Sanders’s Iowa campaign director, said Buttigieg’s appeal to the center would repeat the same mistakes he warned Democrats against.

“We know that centrism and moderates have been losing for a long time, and working people cannot wait for incrementalism. Working people in Iowa, working people in this country are ready for everybody in and nobody out,” Rebik told The Hill in an interview Thursday. “The one way that we defeat Donald Trump is by expanding the electorate and welcoming new voters into our movement.”

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As Biden and Buttigieg stump across the state, Sanders and the two other senators who have a substantial stake in the Iowa caucuses were stuck in Washington, asking questions of House impeachment managers and the president’s lawyers as Trump’s trial drags on.

That's left the field in Iowa to Biden and Buttigieg, who are both seeking to take advantage.

The pointed shots leveled by the candidates stumping through Iowa stand in stark contrast to the television advertising blitz that takes up every spare 30 seconds on broadcast and cable channels across the state.

The Democratic candidates and a few outside groups backing them have spent $72 million on television advertising in Iowa alone, nearly double the amount spent during the 2016 race, according to Advertising Analytics, a nonpartisan firm that keeps track of the television markets. Three candidates — Sanders, Buttigieg and businessman Tom Steyer Tom SteyerTV ads favored Biden 2-1 in past month Inslee calls Biden climate plan 'perfect for the moment' OVERNIGHT ENERGY: Trump administration finalizes plan to open up Alaska wildlife refuge to drilling | California finalizes fuel efficiency deal with five automakers, undercutting Trump | Democrats use vulnerable GOP senators to get rare win on environment MORE — have spent more than $10 million on Iowa ads alone.

Those advertisements almost exclusively feature attacks on Trump, who rallied his fans at a Des Moines arena Thursday night in a pointed show of counterprogramming the Democratic candidates.

“We have to beat him. Joe Biden is the strongest candidate to do it. He beats Trump by the most nationally and in the states we have to win. This is no time to take a risk. We need our strongest candidate, so let’s nominate the candidate Trump fears the most,” a narrator says in Biden’s closing advertisement.

“When someone shows you who they are, believe them. Trump’s life taught him how to get rich on the backs of others. Elizabeth Warren Elizabeth WarrenGOP set to release controversial Biden report Biden's fiscal program: What is the likely market impact? Warren, Schumer introduce plan for next president to cancel ,000 in student debt MORE will be a president who works for you,” Sen. Elizabeth Warren’s (D-Mass.) narrator says.

Buttigieg promises “a bold vision for the next generation” in his ad. “We need to break from the old politics and unify this nation,” he says.

Sen. Amy Klobuchar Amy KlobucharBattle lines drawn on precedent in Supreme Court fight Sunday shows - Ruth Bader Ginsburg's death dominates Klobuchar: GOP can't use 'raw political power right in middle of an election' MORE (D-Minn.), who has risen slowly and steadily in recent polls, promises to “be a president and a commander in chief who restores decency to the White House and gets things done for you.”

Late polls in the race show a jumbled mess atop the field, with Sanders and Biden vying for the top slot. Buttigieg and Warren are trailing, and some polls show Klobuchar with a late surge of momentum.

The Iowa Democratic Party, much maligned after a close caucus result in 2016 left some Sanders fans convinced they had been the victims of a coup, has implemented new rules that could either give a clearer picture of what caucusgoers want or — more likely — muddle the results even further.

The party will release several sets of results, including an initial total of voters aligned with each candidate, akin to a primary, and a final tally of estimated delegate totals. Given the arcane rules that govern who gets delegates, including whether a candidate hits a 15 percent delegate threshold in each of the state’s approximately 1,700 precincts, the outcome could give several contenders the chance to claim momentum.

Rob Sand, the Democratic state auditor who is staying neutral during the caucuses, said the rules could dampen any one campaign’s claim to a clean win.

“Everyone is going to declare victory,” he said.