ST. PAUL  (AP) - Former state Rep. Dan Severson has become the first Republican to declare a challenge to Democratic Sen. Amy Klobuchar in 2012.

Severson, a 57-year-old retired Navy pilot, served four terms in the state House before running unsuccessfully last fall for secretary of state. He announced his candidacy for Senate Monday on the steps of the state Capitol.

Klobuchar is a formidable opponent for Republicans.  She won her seat in a 2006 blowout, and she's maintained strong public approval ratings throughout her term. She had more than $2.5 million in campaign cash as of mid-April.

(Copyright 2011 by The Associated Press.  All Rights Reserved.)