WASHINGTON (AP) — Donald Trump is addressing the Libertarian National Convention on Saturday night, courting a segment of mostly conservative voters that has often been skeptical of the Republican former president while trying to ensure attendees aren’t drawn to independent White House hopeful Robert F. Kennedy Jr.

The Libertarian Party will pick its presidential nominee during the gathering at a Washington hotel that wraps up Sunday. Kennedy, who ran in the Democratic primary before switching to an independent bid, addressed the convention Friday but has indicated he’s not interested in being the Libertarian nominee.

Polls have shown for months that most voters — even a majority of Democrats — don’t want a 2020 rematch between Trump and Democratic President Joe Biden. That dynamic could potentially boost support for an alternative like the Libertarian nominee or Kennedy, whose bid has allies of both Biden and Trump concerned that he could be a spoiler.

Libertarian presidential candidate Gary Johnson won about 3% of the national vote in 2016, when Trump beat Democrat Hillary Clinton in a tight race. Party nominee Jo Jorgensen got only a bit more than 1% during 2020’s exceedingly close contest between Biden and Trump.

Peter Goettler, president and chief executive of the libertarian Cato Institute, suggested in a Washington Post column published this week that Trump addressing the Libertarian convention violated the gathering’s core values and that “the political party pretending to be libertarian has transitioned to a different identity.”

A Libertarian candidate may try to draw support from disaffected Republicans, but also from people on the left who oppose perceived government overreach. Such voters could also gravitate toward Kennedy.

The son of former Attorney General Robert F. Kennedy, he frames himself as a truthteller with a track record of fighting for the middle class against powerful interests. He is also trying to win over conservatives who want to see the national GOP move away from Trump.

His anti-vaccine activism has appealed to some on the right who oppose COVID-19 vaccine mandates. He has also suggested that some of the pro-Trump rioters who stormed the U.S. Capitol on Jan. 6, 2021, may have been prosecuted for political reasons.

Having previously praised Kennedy and once considered him for a commission on vaccination safety, Trump has changed his tone. He suggested on social media that a vote for Kennedy would be a “wasted protest vote” and that he’d “even take Biden over Junior.”

Trump, in office, referred to the COVID-19 vaccine as “one of the greatest miracles in the history of modern-day medicine.” But the former president now says that — should he win in November — he will “not give one penny” to public schools and universities that mandate COVID-19 vaccination. He also accused Kennedy of being a “fake” opponent of vaccines — efforts that could shore up his support among some in his base who might otherwise consider defecting to Kennedy.

In his own speech at the Libertarian convention Friday, Kennedy accused Trump and Biden alike of trampling on personal liberties in response to the pandemic that spanned their presidencies. Trump bowed to pressure from public health officials and shut down businesses, he said, while Biden was wrong to mandate vaccines for millions of workers.

Vaccines, including the COVID-19 vaccine, have been proven to be safe and effective in laboratory testing and in real-world use in hundreds of millions of people over decades. The World Health Organization credits childhood vaccines with preventing as many as 5 million deaths a year.

While no medical intervention is risk-free, doctors and researchers have proven that risks from diseases are generally far greater than the risks from vaccines.

An anti-vaccine group Kennedy led has a lawsuit pending against a number of news organizations, among them The Associated Press, accusing them of violating antitrust laws by taking action to identify misinformation, including about COVID-19 and COVID-19 vaccines. Kennedy took leave from the group when he announced his run for president but is listed as one of its attorneys in the lawsuit.

Biden, meanwhile, has trumpeted winning the endorsement of many high-profile members of the Kennedy family, in an attempt to marginalize RFK Jr.

The advocacy group MoveOn Political Action, which supports Biden, is circulating a mobile billboard around the Libertarian Convention this weekend decrying Kennedy as “extremist,” criticizing the different positions he has taken on abortion and arguing that a vote for Kennedy will ultimately help elect Trump.