House Republicans won’t be losing too much sleep over the retirement of Henry Brown in South Carolina’s First District. Yes, he had a relatively close race against a big-spending challenger last time, but this district is pretty darn Republican. But McCain carried the district with 56 percent last year, and 2010 is not shaping up to be a good year for Democrats in South Carolina. It’s hard to see Democrats winning an open seat race in a district with a R+10 rating in the Cook Partisan Voting Index, much less with Sen. Jim DeMint’s reelection bid at the top of the ticket, much less in a year when the Democrats will want to spend money defending vulnerable incumbents. The question now is who emerges from the scrum of the primary: Carroll Campbell III, son of the former governor, Katherine Jenerette, a primary challenger to Brown in 2008, Paul Thurmond, son of former Sen. Strom Thurmond, and perhaps more…