Sen. John Walsh, the Montana Democrat chosen to fill Ambassador Max Baucus' empty seat, plagiarized at least 25 percent of his master's thesis, according to an embarrassing report from Jonathan Martin at The New York Times. Walsh is up for re-election in November.

In 2007, Walsh wrote his senior thesis for the United States Army War College  on American Middle East policy. According to Martin, Walsh lifted passages word-for-word from books, papers and other sources available online (several examples of the plagiarism are presented here). In about a third of the paper he included footnotes but presented identical or nearly identical passages as his own work. When asked if he'd plagiarized, Walsh said “I don’t believe I did, no.” But one Walsh aide said he'd been going through a rough patch at the time, following the suicide of one of his friends. 

Walsh isn't the first elected official to be accused of plagiarism. Last year, BuzzFeed discovered that Sen. Rand Paul plagiarized passages from his book, Government Bullies, from conservative think tanks and online articles. The Washington Times also dropped him as a columnist because he'd plagiarized some of his columns for the site. 

But this isn't just embarrassing — plagiarism also has a history of tanking politicians' ambitions. In 1988, Sen. Joe Biden's dropped out of the race for president after it was discovered that he's copied a British Labour Party member's speech. Paul wasn't up for re-election, and Walsh is trailing his Republican opponent in the polls ahead of November's election. This isn't going to help.