With all the usual cavaets about a long time until Election Day, it is now hard to see the Republicans picking up any Democratic Senate seats.
When we look at seats the Democrats hope to pick up, it becomes even more clear that the summer months have not been kind to Republicans. Early in the year, Pennsylvania Senator Rick Santorum was the only Republican clearly in trouble. Now he is joined by a growing list of vulnerable colleagues, four of whom trail their Democratic challenger (Burns in Montana, Chafee in Rhode Island, DeWine in Ohio, and Talent in Missouri).
5 seats leaves the Senate with 50 Republicans, 49 Democrats, and 1 Independent (Bernie Sanders, who may be the most strident liberal in the next Congress). One more seat flips the Senate.
It could happen: there are possibilities in Nevada (with Jimmy Carter's son, no less), in Virginia (Jim Webb vs. George Allen), Arizona (Pedersen vs. Kyl), and more distantly, Tennessee (Ford).
Remember, only 1 of these seats has to end with an upset.