Four days: That's how long it took for an embattled Democratic senator to abandon defiance and embrace defeat.

Sen. John Walsh announced Thursday he is dropping out the Montana Senate race following accusations he plagiarized portions of his 2007 master's thesis at the U.S. Army War College, a move that comes just days after he vowed to dig in his heels.

The announcement, which likely doesn't come as that big of a shock to people who have followed the scandal closely, is an about-face for the embattled senator and Iraq veteran who had initially blamed the lifted portions of his paper on post-traumatic stress disorder.

"I'm not a quitter," Walsh said in an interview with NPR on Sunday. "I'm going to continue to fight on behalf of the citizens of Montana."

"I made a mistake on the paper, there's no question about it," he added. "I admit I made a mistake, I accept full responsibility for that mistake, and now I've got to move on."

But it appears that Walsh has since discovered that he cannot, in fact, put the scandal behind him.

“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. 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 said in a statement posted to his campaign website.

“I am grateful for the opportunity to have met countless people in the course of this campaign who have offered support — who know what’s at stake for the future of our great nation. That is why public service is so important to me, and why I look forward to continuing to fight for Montana in the U.S. Senate."

Just four days.

Oh, also, in case you're wondering who will take Walsh's place in the Democratic Party's bid to defeat Rep. Steve Daines, R-Mont., here are a few possible candidates, as reported by the Washington Post:

John Bohlinger. Bohlinger was lieutenant governor of the state under Gov. Brian Schweitzer -- and was a Republican at the time. When Baucus left his seat, Bohlinger ran in the primary to replace him, losing to Walsh in June by more than 40 points.

Nancy Keenan. Keenan is the former superintendent of public instruction in the state and former president of NARAL Pro-Choice America, an abortion access advocacy group. She spoke at both the 2008 and 2012 Democratic presidential conventions.

David Wanzenried. Wanzenreid currently sits in the [Montana] State Senate, representing the area around Missoula. ...

[Former Gov. Brian] Schweitzer. The former governor had reportedly been considering a run for the presidency in 2016, until an article in the National Journal included some colorful quotes from Schweitzer about his views on identifying homosexual people. A Senate bid, which he had previously turned down, might now look more appealing for Schweitzer.

So that's that. Lying and theft can still sink a political campaign in the United States. In 2014. How about that?