Susan Davis

USA TODAY

WASHINGTON — Sen. John Walsh, D-Mont., announced Thursday that he is dropping out of the Senate race after it became clear that he could not overcome the fallout from a plagiarism scandal.

"The 2007 research paper from my time at the U.S. Army War College has become a distraction from the debate you expect and deserve," Walsh said in a statement. "I am ending my campaign so that I can focus on fulfilling the responsibility entrusted to me as your U.S. senator. You deserve someone who will always fight for Montana, and I will."

Walsh is not resigning his Senate seat and will serve out the term that ends in January.

Walsh, an Army veteran, was the Democrats' top 2014 candidate when he was appointed in February to the Senate after Sen. Max Baucus left to serve as U.S. ambassador to China. His appointment was supposed to give him an electoral edge as the incumbent in a tough election climate for Democrats against GOP Rep. Steve Daines.

Daines has consistently led in the polls for the Senate seat.

A New York Times story in late July revealed that Walsh had plagiarized significant amounts of text in a thesis that earned him a master's degree from the Army War College in 2007. The college is conducting a review that could strip him of his degree. Walsh apologized and said it was a mistake and noted that he has suffered from post-traumatic stress disorder related to his war service.

This week, two Montana papers called for Walsh to end his Senate campaign and to focus only on the remainder of his term.

The Democrats' State Central Committee has until Aug. 20 under state law to choose a replacement candidate for the November ballot.

In a conference call with reporters, Montana Democratic Party Executive Director Andrea Marcoccio said a nominee will be selected by the committee, which includes Democratic Party officials and elected officeholders, at a nominating convention in the coming days.

"The Montana Democratic Party looks forward to an open and transparent opportunity for Democrats to come together to decide our new nominee," said Jim Larson, Montana Democratic Party chairman. "As we move forward in this race, we must remember this election is not about one person; it's about Montana."

A Daines victory would bank a seat for Republicans in their battle to take control of the Senate this year. Republicans are heavily favored to win Democratic-held seats in South Dakota and West Virginia, providing three of the six seats they need to capture the majority in the Senate.