Sen. John Walsh (D-Mont.) with son Michael in Washington. (AP Photo/Lauren Victoria Burke, File)

Sen. John Walsh (D-Mont.) just joined the ranks of Sen. Pat Roberts (R-Kan.), physicians Milton Wolf (R) and Monica Wehby (R), former congressman Trey Radel (R-Fla.) and Rep. Vance McAllister (R-La.).

No, none of those political candidates were revealed to have plagiarized large chunks of their thesis, as the New York Times reported about Walsh on Wednesday. But each of them, like Walsh, has had to deal with big negative stories about their pasts this election cycle.

And they won't be the last. As opposition research becomes more sophisticated and technology allows reporters to scrutinize candidates more closely than ever, we're likely to see more of the kinds of stories that plagued these politicians.

Some of these revelations have clearly been more damaging than others. Radel was forced to resign from office after a drug arrest, while Roberts is favored to win another term after a bad residency story. The jury is still out on Wehby, Walsh and McAllister.

In case you missed the Walsh plagiarism scandal or the other bombshells, we recap them for you below in reverse chronological order:

Walsh's essay: The Times reported Wednesday on evidence that Sen. John Walsh plagiarized a substantial portion of a paper he submitted at the United States Army War College, where he received a master's degree in 2007. Pols have survived plagiarism stories before -- just ask Vice President Biden. But Walsh's military record had already come under negative scrutiny, making it much harder for him to get past the story in his reelection campaign. He was already an underdog to Rep. Steve Daines (R) when the week began. Now, he's looking like a real long-shot.

Wehby's stalking accusation: Just as Monica Wehby was picking up momentum ahead of the Republican primary for U.S. Senate in Oregon, Politico reported that she was accused by her ex-boyfriend last year of  “stalking” him and entering his home without his permission. The story became the focal point in the race for weeks, overshadowing everything else Wehby tried to do. She won the GOP nomination anyway and remains a threat against incumbent Sen. Jeff Merkley (D). But it was the kind of story that is likely to stick in the minds of voters all the way to November. 

The "kissing congressman." The Ouachita (La.) Citizen published surveillance video of Rep. Vance McAllister kissing a then-staffer. The congressman is married. And now, his stay in Congress -- he was elected in a special election last fall -- could be brief. First McAllister said he would not run for another term. Then he changed his mind. But there is no shortage of candidates looking to replace him.

Milton Wolf's Facebook comments: Wolf, who is challenging incumbent Pat Roberts for the GOP nomination for U.S. Senate, came under fire for jokes he made online about graphic X-ray images of gunshot victims and others, as reported by the Topeka Capital-Journal. Wolf had been trying to make his medical career a symbol of his outside-of-politics platform. But his credibility was called into question by the revelation, which came shortly after a damaging news about his opponent. (See below.)

Roberts's residency reveal: The New York Times reported that Roberts stays with supporters when he is in Kansas, not in a home of his own. Seeming to be clueless about the potential political ramifications of his residency, the senator even joked, "I have full access to the recliner." Roberts owns a house in suburban Washington. Despite how disastrous the story initially appeared to be for Roberts, it probably won't cost him his job. A lot of that is because Wolf has run a lackluster campaign.

Radel's resignation:  Then-Rep. Trey Radel was arrested for cocaine possession last fall. After pressure from party leaders mounted, the Florida congressman resigned in January. So ended a potentially promising congressional career by a former TV news reporter.