Does Sen. Jim DeMint's departure spell doom for conservatives on the Hill?

It may have been a coincidence, but it certainly seems highly symbolic that, on a day when the chattering class is increasingly buzzing about a likely Republican “cave” on taxes in the "fiscal cliff" negotiations, South Carolina Sen. Jim DeMint announced he is leaving the Senate to head up the conservative Heritage Foundation.

The announcement was unexpected: Senator DeMint's term wasn't scheduled to expire until 2016. But in a way, the move isn’t all that surprising.

Consider: DeMint has been one of the Senate’s most far-right members, a tea party stalwart who, more than almost anyone else in that body, worked to recruit ideological allies and challenge those in his party he deemed insufficiently conservative.

He was known for his early championing of conservative stars like Florida Sen. Marco Rubio and Kentucky Sen. Rand Paul. But in 2012, he also had some high-profile embarrassments – including Todd Akin and Richard Mourdock, two candidates who lost Senate bids in states many Republicans felt they should have won. As Maine Sen. Susan Collins (R) told NBC’s First Read when asked about the “lessons” of DeMint’s tenure: "I think if you're interested in having Republicans control the Senate, you have to back Republicans who fit their state and who can win in a general election, not just in the primary.”

More to the point, DeMint may have decided that changing government in the way he envisions may actually be easier for him to do from the outside than the inside. Lately, some of the most effective pressure on Republicans has come from outside groups like the tea party, the Club for Growth, and of course, the ubiquitous Grover Norquist, head of Americans for Tax Reform and author of the famous no-new-taxes pledge.

As DeMint himself said in his statement announcing his departure: “I’m leaving the Senate now, but I’m not leaving the fight. I’ve decided to join The Heritage Foundation at a time when the conservative movement needs strong leadership in the battle of ideas.” 

Similarly, former DeMint adviser Matt Hoskins told The Fix’s Chris Cillizza: “He sees his role now as working with the grass roots on the outside to bring out real change in Washington.”

Of course, DeMint’s decision may also reflect more practical considerations: Republicans failed to recapture the majority in the Senate, and it's a simple fact that it’s just not as fun to be in the minority. There is also a likely substantial difference in salary (the current president of Heritage reportedly makes more than $1 million a year).

But for now, it seems inevitable that the move will be cast as both a sign of the conservative movement’s limited clout on the Hill – as well as the growing power of its grass-roots networks.