Indiana Rep. Susan W. Brooks endorsed fellow Hoosier Rep. Luke Messer’s Senate bid Wednesday. She’s the first member of the delegation to publicly choose sides in what’s already become a nasty member-on-member primary war between Messer and Rep. Todd Rokita as the GOP tries to unseat the Democratic incumbent Joe Donnelly.

“Luke and I have been friends for a long time, and being his colleague and watching him work up close, I have no doubt he’ll make a great U.S. Senator,” Brooks said in a statement.

“Luke is a proven conservative, but more than that, he is a respected and skillful leader who builds the relationships necessary to get our shared priorities enacted into law,” she added.

As House Republican policy committee chairman, Messer is the fifth-ranking member in leadership. His role in leadership has been a target of attacks from Rokita, who’s trying to run as the more anti-establishment candidate. Brooks’ endorsement could help Rokita boost his own narrative of being the outsider candidate. 

Brooks was elected in 2012, the same year as Messer. She represents a solidly Republican district north of Indianapolis. The third-term congresswoman will serve as honorary chairwoman of a “Women for Luke” team that will travel the state.

Rokita and Messer aren’t alone in the Senate primary. State Rep. Mike Braun, businessman Terry Henderson and lawyer Mark Hurt are also running. 

Inside Elections with Nathan L. Gonzales rates the Indiana Senate race a Toss-up.