Can Republicans take control of the Senate?
This estimates are from Real Clear Politics averages of different polls. But these averages make some assumptions about who will be the Republican nominee and also include some older polls. For example, if Tommy Thompson runs in Wisconsin, he is ahead in the polls. Thompson isn't included yet because he hasn't made a decision to run. The same is true in Washington state, where if Rossi challenges Murray and you look at only the polls done in April, Rossi is clearly ahead. These two races would end up giving Republicans a 51 to 49 majority in the Senate. If Thompson and Rossi do run, that could dramatically increase the odds that Republicans will take the Senate (much more than the 17.5 percent that inTrade currently predicts).
If Tom Campbell wins the Republican primary (and he is currently ahead), the last three polls in that race suggest that he would be exactly tied with Barbara Boxer.