After months of flirting with a possible Libertarian Party run, independent presidential candidate, Robert F. Kennedy Jr., says he will not seek the Libertarian nomination at the party’s convention in May.

Facing steep ballot access challenges running on an independent ticket, Mr. Kennedy had until now refused to rule out a Libertarian run. This weekend he changed his tune.

“Mr. Kennedy has many areas of alignment with the Libertarian Party, including a strong stance on civil liberties and keeping the country out of foreign wars,” a Kennedy campaign official said in a statement to the Sun. “Mr. Kennedy, however, is not contemplating joining the Libertarian ticket. He is running as an Independent candidate and will be on the ballot in all 50 states and the District of Columbia.”

This announcement comes one day after Mr. Kennedy hosted an assembly in Iowa, in which more than 500 eligible voters signed a form to fulfill the Hawkeye State’s ballot access requirements. The campaign has so far achieved ballot access in Utah and has collected the necessary signatures to achieve it in Nevada, New Hampshire, North Carolina, Idaho, Nebraska, and Hawaii.

“We have the field teams, volunteers, legal teams, paid circulators, supporters, and strategists ready to get the job done,” a Kennedy campaign press secretary, Stephanie Spear, said in a statement. “We are exceeding all our benchmarks and will be announcing new states each week.”

The possibility Mr. Kennedy would show up at the Libertarian Party’s convention in Washington D.C. and throw his hat in the race was causing consternation within the party. Although Mr. Kennedy has far more name recognition than any of the handful of candidates running for the party’s nomination this year, he was hardly a shoe-in.

“I don’t think it’s likely at all,” the Libertarian Party’s 2020 vice-presidential candidate, Spike Cohen, told the Sun on Friday of Mr. Kennedy’s chances at winning the party’s nomination.

“He’s been a welcome voice on medical freedom and free speech, but he’s still a believer in bigger government,” Mr. Cohen says. “If the LP nominates someone like him, our purpose ceases to be. We become a third head of the uniparty.”

The Libertarian Party is the third-largest political party in the country. It has gotten ballot access in all 50 states the last few election cycles, and the party’s chairwoman Angela McArdle told the Sun this year the “worst case scenario would be 48 states.”

Ms. McArdle did not return the Sun’s request for comment this weekend. She told ABC News that she would not comment for “at least a few days.”

Several Libertarian Party members who spoke with the Sun said that Ms. McArdle had been courting Mr. Kennedy since they met at Freedom Fest in Memphis last July. Mr. Kennedy spoke at the Libertarian Party of California’s convention in February. In a presidential straw poll there, Mr. Kennedy earned only one of 98 votes, though he wasn’t a declared candidate.

At the Libertarian Party of Texas’s convention this weekend, a group called “Libertarians for Kennedy” sponsored a table. The group’s website details Mr. Kennedy’s libertarian bona fides and has a form to solicit delegates who support Mr. Kennedy.

The Libertarian Party chooses its presidential and vice-presidential candidates by delegate votes at the party’s convention next month. The voting can take multiple rounds until a candidate reaches the 51 percent threshold. There is no clear frontrunner among the declared Libertarian presidential candidates so far. Libertarians for Kennedy did not return the Sun’s request for comment.

“It’s been pretty clear that Angela McArdle has been flirting with the RFK campaign,” the chairman of the party’s Classical Liberal Caucus, Jonathan Casey, tells the Sun. “I think they realized that there’s a cash cow there.”

Ms. McArdle has denied this in interviews, saying that as chairwoman she cannot endorse a candidate. The party is known for its infighting. She told the Sun in January that she appreciates how Mr. Kennedy “took a strong stance against vaccine mandates and the way he stood for medical freedom,” while recognizing policy differences on the minimum wage, guns, and Israel.

Mr. Kennedy this week doubled down on his support for Israel — a position sure to cause problems were he to seek the Libertarian nomination. “There was no political advantage in my choice,” Mr. Kennedy told the Sun in an interview this week. “I did not advocate for Israel out of political calculation, but because no other position makes sense to me.”  

These policy differences are now moot, as Mr. Kennedy will not be seeking the party’s nomination. It would have been an uphill battle for him anyway, and losing the Libertarian nominating contest after a protracted debate on the convention floor could have been a black eye for his campaign. He also wouldn’t be guaranteed to keep his running mate, as the Libertarian Party votes for president and vice president in separate ballots.

“There are several people running for the Libertarian nomination, and just about any of them would represent us better than Bobby would,” Mr. Cohen says. “I believe the LP delegates will rally around one of them to be our next nominee.”