Mitt Romney waded into the crowded Iowa Senate race Wednesday, throwing his support behind state Sen. Joni Ernst (R) in the contested GOP primary.

"As a mother, soldier and proven conservative, Joni has the kind of experience, skillset and discipline it will take to not only win this important seat, but to also take Iowa values to help turn around the mess in Washington," Romney wrote in a fundraising e-mail sent Wednesday morning.

Ernst is one of several candidates vying for the GOP nomination in the race to succeed retiring Sen. Tom Harkin (D-Iowa). She is the unofficial favorite of Gov. Terry Branstad (R) and has the official backing of Lt. Gov. Kim Reynolds (R).

On the Democratic side, Rep. Bruce Braley is the likely nominee. The Fix recently rated the Iowa Senate race as the ninth most likely to flip party control.

This is not Romney's first endorsement of the 2014 cycle. He is also backing Rep. Mike Simpson (R-Idaho), who faces tea party challenger Bryan Smith (R).