Sen. Mitch McConnell's surprise Wednesday announcement that he will step down from leadership in November has launched a high stakes race to replace the longest-serving Senate party leader.

Why it matters: All eyes are on the "three Johns" — GOP Sens. John Barrasso, John Cornyn and John Thune — who are long viewed as the most likely to take up the mantle. But former President Trump looms large.

• Any future leader is certain to inherit a conference divided between its old guard and a newer, emboldened right flank of Trump allies.

Senate Minority Whip John Thune (R-S.D.) is viewed by many in D.C. circles as the most obvious heir with his current No. 2 position, moderate views and fundraising prowess.

• Trump endorsed Thune's challenger in 2022, and Thune only endorsed Trump a couple days before McConnell's announcement.
• Thune's position in leadership could also be viewed as a downside for senators wanting a fresh slate post-McConnell.

Senate GOP Conference Chair John Barrasso (R-Wyo.) has a strong relationship with Trump that could give him an advantage.

• Barrasso was the second senator to endorse Trump, and has also endorsed a slate of the most conservative Senate candidates like Kari Lake, Jim Banks and Bernie Moreno.
• "What I'm focused on is the election that's going to come up in November for president, for the Senate. That's my focus," Barrasso told reporters Wednesday, dodging questions about a leadership run.

Sen. John Cornyn (R-Texas) does not currently have a leadership role — which he could try to play to his benefit in any leadership race after conservative discontent with the recent border deal and foreign aid package.

• He has been critical of Trump in the past, but unlike Thune, never backed any of the former president's primary challengers and endorsed the likely GOP nominee in January.