No one besides Dems ex-State Sen. Staci Appel and some dude Gabriel De La Cerda are running yet, but
The Des Moines Register has a rundown on possible candidates:
Considering:GOP:State Rep. Marry Ann Hanusa (Council Bluffs)
State Sen. Jake Chapman (Adel)
State Rep. Chris Hagenow (Windsor Heights)
State Sen. Charles Schneider (West Des Moines)
State Rep. Rob Taylor (West Des Moines)
State Sen. Jack Whitver (Ankey)
State Sen. and 2010 IA-03 nominee Brad Zaun (Urbandale)
Secretary of State Matt Schultz '
Businessman Jeff Ballenger (Council Bluffs)
Businessman David Oman (Des Moines)
Democrats:Former Gov. Chet Culver
State Sen. Matt McCoy (Des Moines)
Former Iowa Democratic Party Chairman and Des Moines city councilman Michael Kiernan
Physician and health insurance plan president Andy McGuire
Not RunningGOP:State Rep. Peter Cownie
2006 Iowa IA-03 nominee and former State Sen. Jeff Lamberti
Activist Bob Vander Plaats
State Sen. and Senate candidate Joni Ernst
Attorney and Senate candidate Matt Whitaker
Senate candidate Mark Jacobs
Democrats:State Sen. Majority Leader Mike Gronstal
Activist Ed Fallon
Undecided/Could Not be Reached for CommentGOP:Senate Candidate David Young (Van Meter)
West Des Moines Mayor Steve Gaer
State GOP Vice Chairman David Fischer (Altoona)
DemocratsLawyer and Polk County Democrats chairman Tom Henderson (Des Moines)
Des Moines Mayor Frank Cownie
Polk County supervisor Tom Hockensmith
Lawyer and Iowa Democratic Party chairman Scott Brennan
Secretary of Agriculture and ex-Gov. Tom Vilsack
Former First Lady of Iowa and 2012 IA-04 nominee Christie Vilsack