Byrd's passing this past June opened up a Senate seat in a state where President Obama only won 43% of the vote in 2008, and where his approval ratings have consistently been well below the national norm.
Democrats were, however, able to recruit their strongest possible candidate in Gov. Joe Manchin, a relatively conservative Dem who won both of his terms with over 60% of the vote and has enjoyed sky-high approval ratings. Meanwhile, the best that Republicans could get was businessman John Raese, who over the last 26 years has run two unsuccessful campaigns for Senate and one campaign for governor. (Their original top potential recruit, Rep. Shelly Moore Capito, passed on the race.)
[TPM SLIDESHOW: Stranger Than Fiction? TPM Casts The 2010 Midterms Movie]
However, Raese and the GOP made vigorous use of President Obama's heavy unpopularity in the state, combined with its recent conservative trend. Raese then led in the polls about a month ago, and had Manchin seriously on the ropes.
Then two things happened that blunted the GOP's momentum. First, it was revealed that a National Republican Senatorial Committee ad was produced using a casting call for "hicky" actors -- a story that threw the GOP off balance in their efforts to convince the working-class voters of this state that the Republicans were the party for them. Next, Manchin took various steps to distance himself from national Dems, going so far as to release a TV ad in which he shot a cap-and-trade bill, in order to re-establish his identity as a conservative Democrat.
Finally, Manchin attacked Raese's right-wing positions on economics, such as his opposition to the minimum wage and strong support for free trade in this protectionist state. As one ad declared: "John Raese's ideas are crazy."
But now that the Dems have held this seat, they shouldn't rest too easy. Manchin is a conservative Democrat, and made clear at the candidates' debate that he would differ with his party on many issues -- even on such issues as the rewriting or possible repeal of health care reform. If party discipline becomes a major issue in the Senate votes to come, they'll have to work hard to keep his vote.
Late Update: Watch Manchin's victory speech.