With Sen. Olympia Snowe’s startling Tuesday announcement that she would retire, the GOP now must grapple with a key question: Did the centrist Republican lose interest in her Conference or did her Conference lose interest in centrist Republicans?

In the shadow of 2010’s conservative wave election, Snowe had become a “lone wolf” who was “adrift” in her own party, Republicans sources said. Snowe herself conceded Wednesday that she had been so focused on her re-election — and staving off a primary challenge since even before 2010 — that she had lost sight of why she was running in the first place.

Those close to Republican leadership insist that the Conference has not become inhospitable to moderates, but Snowe’s statements paint the picture of an establishment Republican frustrated with the direction of her party and unsure it will change anytime soon.

“It’s about the country and solving problems, and that was my final conclusion. … If we cannot solve problems in this difficult time in our nation’s history, at what point would we? And whether or not that would change, that dynamic. And that’s the problem,” Snowe said Wednesday when asked whether a GOP takeover of the chamber in November would lead to more legislative productivity.

“It was less about my individual amendments or my individual initiatives, but more about the fact [of], ‘Can we solve problems?’ That’s the responsibility of the institution,” she added.

Republicans indicated that Snowe had become less engaged in recent months. For much of the 112th Congress, she rarely spoke up at caucus meetings, and when she did, her most memorable speeches lamented the lack of action on a budget resolution. If her views diverged from her colleagues, they didn’t know it because she rarely voiced them. However, the Maine Republican was effective when she focused on bringing specific initiatives to the floor, particularly from the Small Business Committee, where she serves as the ranking member.

Snowe is in line to take the helm of the powerful Commerce Committee, but sources said the post held little appeal for her. What she really wanted was the Finance Committee gavel, and she didn’t view a promotion on that powerful panel as likely anytime soon, if ever. Sen. Orrin Hatch (R-Utah) likely will become Finance chairman in the next Congress if he wins re-election and the Republicans win the majority.

“She is 65 and wants to have a life — hanging on as chairman of Commerce left her wanting,” said one Republican operative who works on K Street.

Senate Republican aides said Snowe’s complaints are not restricted to centrists. Even the most conservative Members are increasingly annoyed at the gridlock.

Sen. Lindsey Graham (R-S.C.), known both as a deal-maker and a conservative, said he felt there was a looming “rebellion” from rank-and-file GOP Senators waiting to govern.

“This hopefully will be a wake-up call for the Senate,” Graham said of Snowe’s retirement. “There’s a rank-and-file rebellion brewing here … a lot of us are getting tired of just sitting around looking at each other.”

He continued, “It’s not so much about the ideology that holds us back, you can be ideological. [Democratic Sen. Edward] Kennedy was ideological. You could get things done. [Republican Sen.] Jesse Helms was ideological. He was able to get things done. What’s wrong is that we can’t find common ground on the issues that require it, and I think these super PACs are going to make it harder, not easier.”

Sen. Lamar Alexander (Tenn.) voluntarily gave up his GOP leadership post in January because he, too, felt the chamber’s partisanship is too limiting. Rather than retire, Alexander said he hopes to foment change as a rank-and-file Member.

Former Sen. Evan Bayh (D-Ind.), who retired last cycle and is now involved with the centrist group No Labels, said in an interview Wednesday that, during his time in the Senate, it became clear the chamber was becoming more polarized and that outside groups with ample resources were partially responsible.

“In the House, it was the gerrymander that really polarized the institution. In the Senate, it’s the large sums of money from groups with an agenda,” Bayh said.

Republican Senators who were asked Wednesday if Snowe might have felt unwelcome in the Conference because of her moderate politics answered “no.” Instead, they focused on general legislative dysfunction, from a president running against a do-nothing Congress to Majority Leader Harry Reid (D-Nev.) regularly opting for a closed amendment process.

“I’m one of those people,” one GOP Senator said, when asked if the Conference has become inhospitable to deal-makers and bipartisanship. “It’s not so much a problem in the caucus as it is getting things done in the overall Senate. The entire system’s not working.”

Sen. Susan Collins said the Senate’s moderates “are increasingly vilified by both the far left and the far right.”

“We used to be applauded for bringing people together to actually solve problems. Now we tend to be criticized by both sides,” the Maine Republican said. “But that’s not unique to the Republican caucus. Believe me, talking to my friends in the Democratic caucus, they hear the same kinds of criticism.”

But there’s reason to believe Snowe’s troubles were as much with the GOP as they were with the institution.

Sen. Jim DeMint (R-S.C.), speaking to party activists at the 2010 Conservative Political Action Conference in Washington, D.C., made headlines when he said he’d rather a Republican Conference made up of “30 who believe in the principles of freedom than 60 who don’t believe in anything.” It takes at least 41 votes to mount a filibuster.

“Let me make myself even clearer,” DeMint added in his remarks at CPAC. “I’d rather have 30 Marco Rubios in the Senate than 60 Arlen Specters,” referring to the Pennsylvania Senator who switched from Republican to Democrat in 2009.

DeMint said Wednesday that he was disappointed to hear of Snowe’s retirement. The South Carolinian said Snowe was never an obstacle to him and that they agree on fiscal issues. Snowe last year supported DeMint’s Cut, Cap and Balance budget legislation.

But Snowe voted with Democrats in 2010 for Wall Street regulatory reform, for multiple extensions of unemployment benefits and, in the Finance Committee, for the health care reform legislation. She frequently spoke with President Barack Obama and received agreements for her amendments with Reid in exchange for her filibuster-breaking votes.

“I think the idea of the beleaguered moderate is something she’s fostered in her mind,” one Republican aide said.

“It’s not easy being a moderate,” Bayh said of working in the Senate. “The two extremes make you feel like you’re undercutting them, and there’s this illusion that if you just refuse to compromise long enough, the other side will fold and you’ll get your way.”