The Libertarian Party experienced a minor revolt at its biennial convention this weekend over concerns that its leading vice presidential candidate isn't libertarian enough, complicating its efforts to achieve a stronger-than-usual showing in November's presidential elections.

Former Massachusetts Gov. William Weld is running for vice president alongside former New Mexico Gov. Gary Johnson. While Johnson, who was the party's 2012 standard-bearer, is still expected to win the party's presidential nomination when it votes on Sunday morning, party activists have raised concerns over Weld, whom they see as insufficiently committed to the party's small-government, socially liberal platform. Many also expressed concerns over Weld's decision in 2006 to leave the race for governor of New York after securing the Libertarian nomination, leaving the party without a candidate.

Doug Craig, a national board member of the Libertarian Radical Caucus, which advocates for a strict Libertarian platform, said his members do not believe "in a watered-down, weak-kneed message."

"I would say that Weld is disliked by the Radical Caucus," he added. "We believe the way to win election is to change people's minds by putting out the correct message."

Former Rep. Ron Paul (R-Texas), who was the party's nominee for president in 1988, said in a pre-recorded statement that the message "has to be as pure as possible." He went on to denounce Libertarians who argue for "sound[ing] more moderate and more middle-of-the-road," an approach he described as "useless."

Compounding the issue was Weld's rocky introduction to the party. During a vice presidential debate on Friday night, Weld said he would keep the U.S. in the United Nations, a position counter to most Libertarian activists. Making matters worse, he said many people view Libertarians as “unattractive people.” Rather than make the wide-sweeping anti-government pronouncements that appeal to Libertarians, Weld stuck to making boilerplate political statements more reminiscent of a Democratic or Republican candidate. When Weld called for cutting taxes, one attendee screamed "taxation is theft!"

On Saturday, during a question-and-answer session with party officials, Weld came off less like an insurgent politician and more like an aloof Bay State patrician. Asked to describe the difference between Republicans and Libertarians, Weld began by mentioning that former President George W. Bush, loathed in Libertarian circles for his aggressive foreign policy, is "a good friend." When a party member asked about foreign policy, Johnson deferred to Weld, citing his expertise on the issue. Weld began his answer by saying he'd actually been removed from the issue for quite some time.

When another attendee called for reducing the CIA's presence overseas, Weld replied that he was possibly biased in the matter, name-checking Kermit Roosevelt Jr, his "great-uncle-in-law" and a leading CIA figure who helped depose a number of foreign governments, including Iran's democratically elected leader, Mohammad Mosaddegh, in 1953.

John Raoux/ASSOCIATED PRESS

Now, party activists and many convention delegates are calling Weld "Republican lite" and the specter exists of Johnson running with a more unorthodox figure as his running mate. Other candidates for the office include an online radio host and a libertarian activist who, on his website, HustleBear.com, says he hasn't had a steady job since he was "scooping ice cream at Coldstones at 17."

The Johnson campaign has responded to this criticism by playing up the more libertarian parts of Weld's record and arguing that having two former governors on the ticket makes the party move viable in November.

"Going forward, I think [our chances] would be handicapped by 50 percent without Bill Weld," Johnson said during a press availability, saying that "the attention that he garners, the credibility that he brings to this, the fact that he's been a role model to me for all of my life" makes him an indispensable part of the party's plan for November.

"I will not get elected president of the United States if Bill Weld is not my vice presidential candidate," Johnson said. "It's not going to happen, it's just that simple."

Asked if he would drop out of the race if Weld is not the vice presidential nominee, Johnson replied, "[It's like] training for a marathon and I just broke my leg and the marathon is tomorrow. Do I run?"

Pressed by The Huffington Post on whether that amounted to a "no," Johnson responded, "I'm not saying that. I'm just saying I don't want to not put my best foot forward."