When news broke last week that Sen. John Ensign (Nev.) had an affair with a married staffer, his GOP colleagues quickly went into “scandal mode,— making their way through the Capitol complex’s public spaces with a studied determination that only comes with practice.

“It’s a no-comment day,— Sen. Pat Roberts (R-Kan.) quipped on Wednesday as the scandal engulfed Ensign. Sen. John McCain (R-Ariz.) feigned to be suddenly hard of hearing as a reporter pressed him for comment.

The fact that Senate Republicans repeatedly have faced scandal, shifting leadership lineups, deaths and other difficulties has been politically embarrassing — and a distraction for a party still trying to define itself following eight years of the Bush administration.

It has been a hard couple of years for the Senate Republican Conference, starting with the GOP’s electoral collapse in 2006 when they lost control of the Senate. In 2007, Sen. David Vitter (R-La.) became embroiled in the “D.C. Madam— scandal and had to face questions about an inappropriate relationship with a prostitute. In June of that year, Sen. Craig Thomas (Wyo.), one of the GOP Conference’s most beloved members, died of cancer. Then later that summer, Sen. Larry Craig (R-Idaho) was caught in a sex sting in a Minneapolis airport men’s room.

That could be considered a bad stretch by any measure, but the hits kept coming. At the end of 2007, Minority Whip Trent Lott (Miss.) — who lost the top spot in the Conference several years earlier amid an uproar over his comments at then-Sen. Strom Thurmond’s (R-S.C.) 100th birthday party — abruptly stepped down, leaving a major gap within the GOP leadership. Lott was a master of the art of compromise and was a powerful figure within his Conference.

The next year was just as difficult for Republicans. During the spring of 2008, the son of then-Sen. Ted Stevens (Alaska) was implicated in a state corruption scandal — which would ultimately expand to include the Senator himself. Stevens would be indicted, brought to trial and found guilty before year’s end.

Election Day 2008 brought further woes for Senate Republicans, bringing their total two-cycle loss to 16 seats.

Unfortunately for Republicans, 2009 hasn’t been much kinder to them. While Minority Leader Mitch McConnell (R-Ky.) and Republican Conference Chairman Lamar Alexander (Tenn.) struggle to find sure footing to fight the Obama administration and Congressional Democrats, they already have been hit with several setbacks.

First came the sudden defection from the GOP of Sen. Arlen Specter (D-Pa.) following a series of attacks on moderate Republicans by outside party leaders such as Republican National Committee Chairman Michael Steele, followed by Ensign’s sex scandal this month.

Publicly, GOP lawmakers downplayed the impact of this difficult stretch. “We’re fine,— Sen. Susan Collins (R-Maine) said.

But privately, Republicans acknowledged the string of scandals and other misfortunes has been difficult to deal with. “It’s certainly not helpful,— one GOP leadership aide acknowledged.

“It’s Friday. I’m trying to enjoy myself,— one veteran GOP Senate aide joked when asked about the long list of problems that have befallen his party.

Republicans said their luck has been particularly frustrating given their efforts to rehabilitate the party over the past two years. McConnell and Alexander have worked hard to stake out positions for their party on energy and national security, for example. But spending days — or, in the case of Stevens, months — fending off criticism and questions about unrelated issues has been a major unwanted distraction, Republicans said.

Senate Republicans largely praised McConnell’s handling of the Conference, noting that he has remained the one constant in the party’s leadership and has avoided becoming a lightning rod for scandal or complaints himself — which is no small feat for any party leader.

“The one hallmark of McConnell … is that he, as a party leader, is one of the only people in leadership who isn’t a liability for some of his party. [Senate Majority Leader] Harry Reid [D-Nev.] is a liability for his moderates. So is [Speaker] Nancy Pelosi [D-Calif.]. So was [former House Majority Leader] Tom DeLay [R-Texas],— one Republican said.

Republicans said they are simply trying to put this latest scandal behind them — a familiar refrain since 2006.

“Obviously it’s unfortunate what happened here that required change, but I think the new leadership will bring rebranding, which is good,— moderate Republican Sen. Olympia Snowe (Maine) said.

Jessica Brady contributed to this report.