Sharron Angle, the Republican candidate in Nevada, has been improving her position in our forecast in recent days, and for the first time since the spring has better than a three-in-four chance to win her race against Harry Reid, according to the FiveThirtyEight model.

Ms. Angle’s odds improved today on the strength of a CNN poll showing her 4 points ahead of Mr. Reid. The lead, while slight, is her largest since January in a poll from a firm other than Rasmussen Reports. Moreover, CNN’s poll, unlike some others, included Nevada’s unique option for none-of-these-candidates in their poll, as well as the name of Scott Ashijan, who is running under the banner of the Tea Party on the Nevada ballot, although he lacks the support of most Tea Party affiliated groups. A separate version of CNN’s poll, which tested solely Ms. Angle and Mr. Reid, found the Republican with a slightly larger lead of 6 points, and with over 50 percent of the vote.

The polling has been a little bit sparse in Nevada relative to some other states; only CNN and Rasmussen Reports, which also now shows Ms. Angle with a 4-point lead, have released surveys in the past 10 days. Still, at least on the basis of the public polling, it is reasonable to consider the race as leaning toward Ms. Angle.

Republican chances of a Senate takeover, however, are actually down from yesterday’s forecast because of problematic polling for them in another state, West Virginia. There, a new survey from Rasmussen Reports, which had generally shown poor numbers for the Democrat Joe Manchin, now shows him 3 points ahead of John Raese instead. While West Virginia could use more polling, the situation is analogous to Nevada in some ways, in that the state has at least tentatively moved in one direction after having been a tossup for some time. The model now makes Mr. Manchin a 77 percent favorite.

Because Republicans have to virtually sweep the competitive Senate contests to win control of the chamber — not just split the competitive contests with the Democrats — it does not particularly help them when one race (Nevada) moves toward the Republicans at the same time another (West Virginia) moves an equal amount toward the Democrats. It now looks more likely, for instance, that Republicans could win the Senate race in Washington while losing the one in West Virginia. That would deprive them of the Senate unless they could also win California, where their odds have grown somewhat more remote. (There were two new polls released today in California, but they confirmed the model’s existing impression of the race, which is that Democrat Barbara Boxer has about a 5-point lead and is slightly better than 90 percent to win.) Thus, Republican chances of winning the Senate dropped over all to 12 percent from 14 percent.