(CNN) - Sen. John Walsh dropped out of the Senate race in Montana on Thursday amid allegations of plagiarism, a senior Democratic source familiar with the senator's thinking confirmed to CNN.
The move further hurts Democratic chances of maintaining control of the Senate. Republicans need a net gain of six seats in November to take the majority.
Washington (CNN) – Under fire for plagiarism, Democratic Sen. John Walsh of Montana is now feeling the pressure at home.
Newspapers from the two largest cities in Montana are calling for Walsh to end his Senate campaign in light of charges that he plagiarized part of a paper needed to complete his master's degree at the Army War College.
(CNN) – The Defense Department’s inspector general will review the academic investigation of plagiarism allegations against Sen. John Walsh.
The Montana Democrat is accused of not properly attributing certain material in a paper to complete his master's degree at the Army War College.
updated at 3:25pm ET
(CNN) - A significant portion of a paper Montana Sen. John Walsh had to complete to obtain his Master’s degree was taken directly from two sources and given no attribution, according to the New York Times.
At least one-quarter of the 14-page paper, “The Case for Democracy as a Long Term National Strategy,” from the United States Army War College was copied from a Carnegie Endowment for International Peace report and a 1998 Harvard scholar's essay, the Times reported.
Walsh, an Iraq War veteran and former head of Montana’s National Guard, completed the paper in 2007. He was 46.
Nearly 24 hours after the story broke, his re-election campaign released a full-bore defense, laying out more than a dozen accomplishments and awards from his 33-year military career. The campaign didn’t deny the plagiarism but said it wasn’t deliberate.
"He acknowledges the citations were not all done correctly, but that it was an unintentional mistake," the statement said.
Walsh separately told the Associated Press that he was suffering from post-traumatic stress after his Iraq deployment. His office said he commanded an infantry battalion in 2004-05.
His office said the difficult period was not an excuse for the plagiarized portions of the paper.
The damning report could impact not only Walsh’s election chances this November, but also the Democrats’ odds of maintaining control of the Senate.
Walsh stepped down as Montana's lieutenant governor after he was appointed to the Senate in February to replace longtime Democratic Sen. Max Baucus, who was appointed Ambassador to China. Walsh is running in November's midterm election for a full six year term in Senate.
In the conservative state of Montana, Republicans pegged the race as winnable. The GOP must win six seats currently in Democratic hands to win back control of the Upper Chamber.
Even before the plagiarism allegations broke, two of the top non-partisan political handicappers gave the edge in the race to the GOP candidate, Rep. Steve Daines. The Cook Report listed the race as “lean Republican” and the Rothenberg Report rated the contest as “toss up/tilt Republican.”
In a statement, the Democratic Senatorial Campaign Committee defended Walsh.
"John Walsh is a decorated war hero and it’s disgusting that Steve Daines and Washington Republicans are going to try denigrate John’s distinguished service after multiple polls show him gaining. Steve Daines should immediately denounce these latest smears and call for an end to all attacks on John Walsh’s record protecting Montana and serving his country," said DSCC press secretary Justin Barasky.
CNN's Paul Steinhauser contributed to this report.
Washington (CNN) - Hours before Montana Democratic Lt. Gov. John Walsh gets sworn into the U.S. Senate, he's coming under attack by national Republican groups.
The National Republican Senatorial Committee went up early Tuesday with a website titled "Where's Walsh-o" that's critical of the new senator. And American Crossroads, the pro-GOP independent super PAC co-founded by Karl Rove, plans to welcome Walsh into the Senate with an attack ad that's set to run back in Montana.
(CNN) - Montana Lt. Gov. John Walsh now has the job he's already been running for: U.S. senator.
Montana Democratic Gov. Steve Bullock Friday named Walsh, a fellow Democrat, to fill the remainder of the term of Sen. Max Baucus, who was overwhelmingly confirmed Thursday as U.S. ambassador to China.
Washington (CNN) - A conservative group that's spent millions attacking Democrats over the new health care law this election cycle is going up with a new TV commercial supporting a Republican congressman in Montana who's running for that state's open U.S. Senate seat.
The ad by Americans for Prosperity thanks Rep. Steve Daines for his fight against the Affordable Care Act, better known as Obamacare.
(CNN) - Following former Gov. Brian Schweitzer's surprising decision not to run for an open Senate seat next year in Montana, another high profile Democrat from the state has declined to jump into the race.
Stephanie Schriock, the president of EMILY'S List, a group that works to get Democratic women elected to public office, announced Tuesday she will not run for the Senate in 2014.
Updated 9:58 a.m. ET, 7/15
(CNN) - In a surprising twist for the 2014 midterm elections, former Democratic Gov. Brian Schweitzer of Montana will not run for the U.S. Senate as expected, according to a source familiar with his decision.
Schweitzer was widely considered to be the Democratic frontrunner to campaign for the seat and keep it in Democrats' hands after the current holder, Sen. Max Baucus, retires at the end of his sixth term.