OAKLAND, Calif. (AP) – Robert F. Kennedy Jr. plans to announce his running mate Tuesday as he races to secure a place on the ballot for his independent campaign for president.

In advance of an event Tuesday in Oakland, Kennedy and his aides have circulated the names of several contenders, including celebrities with no political experience. Those names include NFL quarterback Aaron Rodgers and “Dirty Jobs” star Mike Rowe as well as former Minnesota Gov. Jesse Ventura. Speculation most recently has centered on Nicole Shanahan, a lawyer and philanthropist who bankrolled a Super Bowl ad for Kennedy.

“This announcement is really going to shake up the political establishment,” Kennedy said in a video he posted on social media last week.

Kennedy’s campaign has spooked Democrats, who are fighting third-party options that could draw support from President Joe Biden and help Republican former President Donald Trump. As they head into a 2020 rematch, Biden and Trump are broadly unpopular with the U.S. public and will compete for the votes of people who aren’t enthusiastic about either of them.

Without the backing of a party, Kennedy faces an arduous task to get on the ballot, with varying rules across the 50 states. He’s picking a running mate now because about half of the states require him to designate one before he can apply for ballot access.

The requirement is already bedeviling Kennedy’s ballot access effort in Nevada, where Democratic Secretary of State Francisco Aguilar said in a March 7 letter to independent candidates that they must nominate a vice presidential candidate before collecting signatures. The letter came days after Kennedy’s campaign announced he’d collected enough signatures in the state. If Aguilar’s opinion survives a likely legal challenge, Kennedy will have to start again in collecting just over 10,000 signatures in the state.

“This is the epitome of corruption,” said Paul Rossi, a Kennedy campaign lawyer, in a statement Monday, accusing Aguilar of doing the bidding of the Democratic National Committee.

Kennedy has secured access to the ballot in Utah. He and an allied super PAC, American Values 2024, say they’ve collected enough signatures to qualify in several other states, including swing states Arizona, Nevada and Georgia, but election officials there have not yet signed off.

Kennedy is a descendant of a storied Democratic family that includes his father, Robert F. Kennedy, who was a U.S. senator, attorney general and presidential candidate, and his uncle former President John F. Kennedy.

He began his campaign as a primary challenge to Biden but last fall said he’d run as an independent instead.

Kennedy was a teenager when his father, known as RFK, was assassinated during his own presidential campaign in 1968. RFK Jr. built a reputation of his own as an activist, author and lawyer who fought for environmental causes such as clean water.

The Democratic National Committee, meanwhile, is gearing up to take on Kennedy and other third-party options, including No Labels, a well-funded group working to recruit a centrist ticket. The effort is overseen by veteran strategist Mary Beth Cahill, whose resume includes chief of staff to the late Sen. Edward M. Kennedy of Massachusetts, another of RFK Jr.’s uncles.

Many Democrats blame Green Party candidates for Al Gore’s loss to George W. Bush in 2000 and Hillary Clinton’s loss to Trump in 2016.