WASHINGTON – The surprise resignation of Republican Sen. Jim DeMint of South Carolina on Thursday could prove to be a marker for a decline in the influence of the tea party movement he has helped lead.

His departure from Congress, effective next month, comes as the political winds appear to be blowing against the 61-year-old lawmaker and the movement he has spoken for. Some of the movement’s most fiery members lost re-election bids last month, including Reps. Allen West of Florida, Joe Walsh of Illinois and Chip Cravaack of Minnesota. Earlier this month, the House GOP leadership unceremoniously removed three conservatives from key committee assignments.

And polls have shown declining support for the movement. A wide survey in DeMint’s very conservative home state, released this week, found that more South Carolinians now disapprove of the tea party movement than approve of it. Even among the state’s Republican voters, fewer than 1 in 12 said they considered themselves tea partyers, according to the Winthrop University poll.