President Trump promised to commute the prison sentence of dark web drug marketplace founder Ross Ulbricht at the Libertarian Party convention in Washington Saturday evening, signaling how seriously Mr. Trump is taking the liberty vote as he campaigns to win the presidency in what is expected to be a close election.

Mr. Trump endured boos and chants of “liar” and “panderer” as he made his pitch to a packed hotel ballroom composed of Libertarians convention goers and MAGA fans — many donning red hats — who’d traveled just to hear the former president speak. 

“Free Ross Ulbricht” topped the list of issues the Libertarian Party said they hoped Mr. Trump would address in his speech to the convention. Libertarians advocate for drug legalization and freedom from fiat currency. Ulbricht’s conviction and life sentence in 2015 for several charges, including drug laundering, for running the cryptocurrency drug sales site, Silk Road, has become a cause célèbre. Many in the audience held “Free Ross” signs.

“If you vote for me, on Day One I will commute the sentence of Ross Ulbricht,” Mr. Trump said to a standing ovation. “We will get him home.”

For a candidate who once praised the Filipino president Rodrigo Duterte for doing “an unbelievable job” in executing drug dealers, Mr. Trump’s promise to free Ulbricht is a serious olive branch to libertarian voters. He also promised to put a libertarian in his cabinet and in other high-profile administration positions.

The promised concessions are a sign Mr. Trump realizes he needs a certain percentage of the libertarian vote to win in November. He lost the swing states of Arizona, Georgia, and Wisconsin to President Biden in 2020 by fewer votes than were cast in those states for the Libertarian candidate, Jo Jorgenson. Those states cost Mr. Trump the election.

“In the past year I’ve been indicted by the government on 91 different things, so if I wasn’t a libertarian before, I sure as hell am a libertarian now,” Mr. Trump joked.  “I am asking for the Libertarian Party’s endorsement or at least lots of your votes.”

This overt bid for the Libertarian nomination elicited more boos from the crowd. Mr. Trump’s speech came one day after independent presidential candidate Robert F. Kennedy Jr. addressed the Libertarian convention, attacking Mr. Trump for violating Americans’ constitutional rights during the Covid pandemic.

“Many probably do not forget some of Trump’s policies during COVID, whether it’s vaccine related or locked down related, and they may not be ready to forgive and forget,” a Republican strategist, Matthew Bartlett, told the Sun.

The Libertarian Party chairwoman, Angela McArdle, advised her party ahead of time to keep the room civil since libertarians believe in free speech and “this is the Libertarian national convention, it’s not Ben Shapiro at Berkeley. We’re not Antifa.” Yet delegates who spoke with the Sun said they expected a raucous room.

“These are libertarians — of course they’re going to boo. They boo their own people,” a delegate from Montana, Melissa Wong, told the Sun.

“Trump knows he needs the liberty movement. If the liberty movement votes for the Libertarian Party candidate in November, that could be his margin of defeat,” antiwar activist and Libertarian Institute director, Scott Horton, told the Sun. “He’s come crawling to us to ask for our support.”

Mr. Horton isn’t buying Mr. Trump’s promises, but he says Mr. Trump making them is a win for the party nonetheless. Members of the Libertarian Party were divided on whether Mr. Trump’s speaking engagement would help or hurt the party.

“I’m not a Trump fan. I want Trump in jail for pushing the Covid regime and Operation Warp Speed,” Libertarian presidential candidate, Josh Smith, told the Sun. “But we have more media and press eyes on us than we have ever had in our 50 years of existence because of this.”

“We got a major political party candidate to say that he would free Ross Ulbricht,” Libertarian presidential candidate, Michael Rectenwald, said at a news conference after Mr. Trump’s speech. “We moved the needle toward liberty.”

Many Libertarians, though, castigated Ms. McArdle, for inviting Mr. Trump, as well as Mr. Kennedy and Vivek Ramaswamy, to the convention. “We could get a lot of attention by burning the hotel down too. That would gain us a lot of attention but it’s not good attention,” a chairman of the party’s Classical Liberal Caucus, Jonathan Casey, who opposes the party’s Mises Caucus-led leadership, told the Sun.

Libertarian presidential candidate Chase Oliver told the Sun he worried Mr. Trump’s speaking engagement and media coverage would cause “brand confusion” to unsavvy voters. He also said he didn’t believe Mr. Trump would follow through on any promises.

 Mr. Trump took all the boos and displays of performative displeasure in stride, asking a fundamental question of his audience about the role of their party, particularly in presidential politics: Is the Libertarian Party a political party whose goal is to elect candidates or is it a messaging platform?  

Mr. Ramaswamy, now a close advisor to Mr. Trump, asked a similar question when he spoke at the convention Friday night, pitching Mr. Trump as libertarians’ best shot at actualizing policies for freedom.

“So what is the purpose of the Libertarian Party getting 3 percent?” Mr. Trump asked. “You want to make yourselves winners. It’s time to be winners.”

Mr. Trump’s speech may pay off for him. The Sun spoke to a handful of Libertarian Party delegates who said they are considering voting for Mr. Trump. An alternate delegate from New Jersey, Tatiana Moroc, told the Sun right after the speech, “He has my vote because he’s the only hope we have. Libertarianism is great but we’re not winning any elections.”

Despite all the party infighting over Messrs. Trump and Kennedy attending the convention, Ms. McArdle’s gamble in doing so appears to have paid off. She won reelection to another two-year term as chairwoman of the party shortly before Mr. Trump took to the stage.

After Mr. Trump’s speech, a handful of Libertarian presidential candidates held a press conference on the same stage where Mr. Trump had just finished. Most of the crowd didn’t stay to hear them speak.