Iowa Lt. Gov. Kim Reynolds (R) announced Tuesday that she won't run for Senate in 2014, leaving the GOP still in search of a standard-bearer in the open-seat race.

In an e-mail to supporters Tuesday afternoon, Reynolds wrote that, "after serious and thoughtful discussions with family, friends, supporters and constituents, I have decided to remain as Lieutenant Governor and will not seek a seat in the United States Senate."

"I truly believe that my focus needs to remain on being Lieutenant Governor and working with Governor Branstad as we continue to move Iowa forward," she added.

Reynolds had expressed interest in running for Senate, but only if Rep. Steve King (R-Iowa) didn't run. King hasn't made his plans known yet, but a Reynolds aide said she has no advance knowledge of his intentions.

Other potential candidates include state Agriculture Secretary Bill Northey, former U.S. attorney Matt Whitaker and state Sen. Brad Zaun.

On the Democratic side, Rep. Bruce Braley is off to a fast fundraising start, pulling in more than $1 million in the first quarter.