Sen. John Cornyn (R-TX) told donors he’s raised $400 million over the last two decades as he seeks to prove he can fill Minority Leader Mitch McConnell‘s (R-KY) shoes in the Senate.

In a letter to supporters on Tuesday, Cornyn announced that he reached the “extraordinary milestone” of $406 million raised since his election to the Senate in 2002, of which $325 million has gone to candidates or the party apparatus.