Senate Minority Leader Mitch McConnell’s shaky health is in the news again after he was unable to speak for more than 30 seconds while taking questions from reporters on Wednesday.

McConnell, who is 81, had a similar incident just a month ago. And he spent five days in the hospital in March after suffering a rib fracture from a fall.

McConnell’s ability to continue as Republican leader in the Senate was already in question after the first two health scares. Those questions will grow louder now, despite his earlier insistence that he would complete his term as leader.

Here are the three Republican senators — all named John — who might replace McConnell as the leader of their party in the upper chamber of Congress. McConnell has been one of the longest-serving and most consequential Senate leaders in U.S. history.

Sen. John Thune

The 62-year old South Dakotan has been the No. 2 Republican in the Senate since 2019. He is a mild-mannered politician with a moderate streak. And he has been critical of former President Donald Trump.

Thune contemplated leaving the Senate in 2021 but then decided to run for reelection in 2022, a race he easily won.

Thune has been in the Senate since 2005. He considered running for president in the past, most notably in 2012, but since then he has focused on Senate service. He led the Senate Republican Conference for many years and the Senate Republican Policy Committee, both of them consensus-building roles.

Sen. John Cornyn

Cornyn, 71, from Texas, has been in the Senate since 2003. He is a former associate justice of the Texas Supreme Court who went on to serve as attorney general of that state as well.

Cornyn was the No. 2 Senate Republican — a position known as the whip — for six years before Thune took over the role. Unlike Thune, Cornyn has also led the campaign arm of the Senate GOP, focusing on helping his party win elections. He is savvy, with sharper-edged politics than Thune.

Cornyn was at one point considered a nominee for the Supreme Court.

Sen. John Barrasso

Barrasso, 71, hails from Wyoming, and is most likely to move into the second Republican spot if McConnell has to step down from leadership or the Senate.

But if neither Thune nor Cornyn can gain the votes from their fellow Senate Republicans to win the top job, Barrasso would be in the running.

Barrasso was appointed to the Senate in 2007 to replace Sen. Craig Thomas after his death. Since then he has moved up the ranks of Republican Senate leadership, chairing the Republican Policy Committee after Thune and then taking over the leadership of the Senate Republican Conference after Thune became whip in 2019.