Biden builds machine to attack RFK Jr.

Why it matters: Those contrasting approaches are coming into focus as RFK Jr. — who's polling better than any independent candidate since Ross Perot in 1992 — faces increasing scrutiny.

Zoom in: Trump's 2016 margin of victory over Hillary Clinton in three key states — Michigan, Pennsylvania and Wisconsin — was smaller than the total number of votes that Green Party candidate Jill Stein won in them.

• This time, Kennedy threatens the Biden campaign's premise that the election is a choice between Biden's stability and Trump's chaos and divisiveness.
• So Biden's campaign and the Democratic National Committee have dedicated a team of staffers and consultants to try to diminish Kennedy.

The DNC argues that RFK Jr. is a "stalking horse" for Trump who shares a megadonor — businessman Tim Mellon — with the former president. Mellon has given $20 million to Kennedy's super PAC and $15 million to Trump's MAGA Inc. this election cycle.

• The White House also notes that the Kennedy family — royalty in Democratic politics — has been critical of RFK Jr.'s bid.
• Maria Shriver, the niece of the late Robert F. Kennedy, was invited to Biden's State of the Union speech, and Biden posed for a photo with 50 Kennedy family members on St. Patrick's Day. The not-so-subtle message: The Kennedys support Biden over one of their own.
• The DNC filed an FEC complaint against RFK Jr.'s campaign, alleging that it's receiving an illegal contribution from his super PAC, American Values 2024, because the group is trying to get him on the ballot in several states.
• "We know the GOP is already working to prop up third-party candidates like Robert Kennedy Jr. to make them stalking horses for Donald Trump," DNC spokesperson Matt Corridoni told Axios.
• "We're going to make sure voters are educated and we're going to make sure all candidates are playing by the rules."

The other side: Top Trump allies say they're watching RFK Jr. closely but — for now — aren't planning to burn resources to go after him.

• Trump's campaign initially called RFK Jr.'s independent bid "a vanity project for a liberal Kennedy." The Republican National Committee put out a list of reasons why he should be viewed as a "radical Democrat," noting his call to cut back on fossil fuels.
• But now Trump's team sees Kennedy as hurting Biden's standing in polls more than hurting Trump.

• Trump allies acknowledge that Kennedy's criticism of vaccines is attractive to some of Trump's base. But they think that if necessary, they could easily hit Kennedy on his stance on the environment and other issues.

Reality check: Kennedy's campaign still needs to navigate a constellation of state laws to get on more states' ballots.

• It's filed lawsuits in some states, and started political parties ("We the People" and "Texas Independent Party") in others.
• Kennedy is officially on the ballot in just one state now — Utah. His campaign claims it has enough signatures in New Hampshire, Nevada and Hawaii to get on those states' ballots.
• American Values 2024 says it has collected enough signatures to get him on ballots in other key states, including Michigan, Arizona and Georgia.

Driving the news: Kennedy aims to announce his running mate on Tuesday.

• His team has floated NFL quarterback Aaron Rodgers and former wrestler/Minnesota governor Jesse Ventura as possibilities, but recent speculation has focused on Nicole Shanahan, a tech financier and major donor to his PAC.
• "Mr. Kennedy plans to take votes from both President Biden and former President Trump," Stefanie Spear, press secretary for the Kennedy campaign told Axios.
• "Of course the DNC is worried. Kennedy has the highest favorability among the candidates and outpaces Presidents Biden and Trump among independents."