Kentucky Gov. Andy Beshear is giving Sen. Mitch McConnell, R-Ky., an ultimatum, demanding that he prove he’s still capable of serving in the U.S. Senate — or resign.

“As Governor of the state you serve, I am calling on you to directly and verbally address the people of Kentucky and provide proof of your capacity to serve, or reign,” Beshear wrote.

Failing that, the Democratic governor said he’ll call on Senate Majority Leader John Thune, R-S.D., to “investigate” McConnell’s condition and “begin the process if warranted” of replacing him in the Senate. Beshear wrote a separate letter to Thune outlining the same demand.

The letter from Beshear comes after McConnell was hospitalized in Washington on June 14 and hasn’t been seen in public since. McConnell’s office has released two photos and written statements saying he suffered a fall, amid public pressure to be transparent and conspiracy theories about the nature of his condition condition.

“It has now been 43 days since news of your hospitalization,” Beshear wrote to McConnell. “During that time you have cast zero votes, engaged in no official activities, and aside from two photos and corresponding statements, have made no effort to communicate with your Kentucky constituents or the nation. Even the attending physician’s written statement does not discuss your actual condition, including whether you can speak, reason, or carry out your duties as a senator.”

McConnell’s office declined to comment on Beshear’s letter.

Asked to comment on Beshear’s calls to investigate McConnell’s condition, Thune said Tuesday that it’s not his issue to resolve.

“I’ve seen that letter, but in any event, I think that’s an issue really that’s between Senator McConnell and the people of Kentucky,” Thune told NBC News. “I mean, if the governor wants to, I’m not sure what his prerogatives are in that case. But that’s where the issue should be resolved.”

Beshear, a potential 2028 presidential candidate, issued his letter as McConnell has faced calls from the left and right to be more forthcoming. He isn’t the first senator to face a health-related absence from the Senate, and the chamber doesn’t have transparency rules for members in that position.

“We have seen rampant speculation across social media and elsewhere, it could all be fully avoided, and it’s all within Senator McConnell’s power,” Beshear told reporters on Tuesday. “But because he won’t do that, the fact is that we don’t know.”

“I hope everything’s okay, that he’s competent to serve, but asking someone to prove that to their constituents isn’t a big or a heavy lift,” he added. “It’s not being invasive. You’re one of two U.S. senators that are supposed to represent Kentucky in Washington. Just talk to the people.”

In most states, governors appoint a new senator when one of the seats in their state is vacant, but not in Kentucky, where state law specifies that a special election must be held instead.

McConnell has already announced his intention to retire at the end of his current term, which expires at the end of 2026. Rep. Andy Barr won the Republican primary to succeed him earlier this year and is favored to win in the red state.