Sen. Bernie Sanders (I-Vt.), a 2020 White House hopeful, underwent a procedure to have two stents inserted to address an arterial blockage after experiencing chest discomfort during a campaign event on Tuesday, aides said.

Jeff Weaver, a senior adviser to Sanders's campaign, said in a statement on Wednesday that the Vermont senator would spend the next few days recovering from the procedure, and that his campaign events would be canceled until further notice.

"Sen. Sanders is conversing and in good spirits," Weaver said. "He will be resting up over the next few days. We are canceling his events and appearances until further notice, and we will continue to provide appropriate updates."

Sanders's campaign also canceled a recently announced $1.3 million television ad buy in Iowa, according to Advertising Analytics, a firm that tracks ad spending. The spot was slated to begin airing on Thursday. A spokesperson for Sanders, however, said that the move was "just a postponement."

At 78, Sanders is the oldest candidate in the presidential race. He has experienced a number of ailments over the years, including hernias and gout. But his allies have long insisted that he's in good health, often pointing to the energy he exhibits on the campaign trail.

During his first run for president in 2016, Sanders's campaign released a letter from his longtime doctor, congressional physician Brian Monahan, asserting that the senator was in "very good health." That letter also noted that Sanders had no history of cardiovascular disease.

He has not yet released his medical records, though he has said he will do so eventually.

The new procedure could raise questions about Sanders's age and physical health as he seeks the nomination to take on President Trump in 2020. He conceded in an interview last year that his age would likely be "part of a discussion" in his presidential bid, but said that he remained in good health.

"I'm very blessed with my health," he told Politico at the time.

Throughout his campaign, Sanders has sought to project himself as physically active. His campaign has occasionally posted photos of him playing sports, like basketball, and he recently pitched a softball game against members of the press in Iowa.

News of the new heart procedure came a day after Sanders's campaign announced a staggering $25.3 million fundraising haul in the third quarter of the year, the largest sum disclosed by any candidate so far.

As news spread on Wednesday that he had undergone the procedure, several of the senator's rivals for the Democratic presidential nomination wished him well in his recovery.

"Thinking of @BernieSanders today and wishing him a speedy recovery," Sen. Kamala Harris (D-Calif.) tweeted. "If there's one thing I know about him, he's a fighter and I look forward to seeing him on the campaign trail soon."

"Glad to hear my friend @BernieSanders is doing well and in good spirits-wishing him a speedy recovery," Sen. Cory Booker (D-N.J.) wrote on Twitter.

- Reid Wilson contributed to this report, which was updated at 12:23 p.m.