Missouri Republican Ann Wagner quickly formalized her 2012 campaign for Congress Tuesday in the wake of Rep. Todd Akin's (R-Mo.) decision to make a bid for Senate.

Late last month, Wagner launched an exploratory committee ahead of a likely run for the 2nd district seat, citing "the likely event" that Akin would opt for a 2012 Senate bid.

"I have been traveling the district and listening to the people in our district about the strong, effective, conservative leadership we need in the Congress," Wagner said in a statement posted on her website Tuesday. "The encouragement and enthusiasm I've received to run for Congress has been overwhelming."

Republican Ed Martin is already in the open-seat race for Akin's 2nd congressional district seat. Earlier this month, Martin pulled out of the 2012 Senate race against McCaskill in favor of another House run. Last fall, Martin nearly defeated Rep. Russ Carnahan (D-Mo.) in the state's 3rd congressional district.    

As expected, Akin entered the Senate race Tuesday, setting up a potentially bruising campaign for the Republican nomination to face first-term Sen. Claire McCaskill (D-Mo.).

The six-term St. Louis-area Republican joins a field that includes former state Treasurer Sarah Steelman (R).