Retired Army Capt. Dan Feehan has filed to run as a Democrat in Minnesota's 1st District. Campaign photo submission.

An Iraq War veteran who later had a high-level job at the Pentagon will run as a Democrat for an open Minnesota congressional seat expected to be one of the nation's costliest House races in 2018.

Dan Feehan, 34, filed paperwork Thursday to make his candidacy official. He planned a kickoff on Monday. A campaign aide said Friday that Feehan was withholding comments for publication or broadcast until that day and wouldn't consent to an interview for immediate use.

The 1st Congressional District race in southern Minnesota will be closely watched because DFL Rep. Tim Walz is running for governor rather than re-election. Walz narrowly hung on for a sixth term in a district that Republican President Donald Trump carried.

Feehan is the fifth DFLer to declare a candidacy. So far only one Republican, James Hagedorn, is in the running on that side after having sought the seat in the prior two elections.

According to materials provided by the campaign, Feehan was raised in Red Wing and now lives in North Mankato. His biography says he served two tours in Iraq between 2005 and 2009, receiving military commendations along the way. He worked his way up to the rank of captain and later held a deputy assistant secretary position in the Department of Defense. Along the way, Feehan was a fellow in Democratic President Barack Obama's White House.

Feehan and his wife, Amy, are raising two young boys.