Sen. John Cornyn (R-TX) has raised $18.3 million this cycle to help boost Republican Senate incumbents and hopefuls, raising more than Sen. John Thune (R-SD) as both men compete to become the next Senate Republican leader.

Both senators are working to raise money as they compete for the votes of their conference after Senate Minority Leader Mitch McConnell (R-KY) announced he would step down as leader in November, setting off a battle over fundraising and ties with high-dollar donors.