Cornyn may be facing his toughest Senate re-election fight yet in a primary against state Attorney General Ken Paxton — and the field could continue to grow.

Republican Texas Sen. John Cornyn is not bowing out without a fight. The Texas incumbent, who is seeking a fifth

CNN reports, Cornyn brought in $3.9 million to Paxton’s $2.9 million between April and June. Paxton is challenging Cornyn in what’s shaping up to be one of next year's hottest-contested primaries.