THEY'RE ALL IN PLAY:

For Democrats, Senate Still a Possible Nightmare (Stuart Rothenberg, 9/30/10, Roll Call)

O'Donnell's primary victory notwithstanding, Republicans are still headed for major Senate gains, and a 10-seat gain isn't impossible.

With a month to go until Nov. 2, Republicans have a clear advantage in five seats held by Democrats, with another five seats still in play.

Unless things change, Republicans will likely hold all 18 of their seats up this cycle. [...]

GOP nominees have a solid advantage in three states: North Dakota, Arkansas and Indiana. They have an advantage in the polls -- and a momentum advantage -- in two other states: Pennsylvania and Wisconsin.

Polling in Illinois has been close for weeks, but with Republican Bill Brady running ahead in the gubernatorial race and Republican Congressional candidates overperforming in a number of parts of the state, Republican Rep. Mark Steven Kirk seems more likely than not to win the Senate race.

If all of those races fall into place as expected, they add up to a gain of six seats for Republicans, with six other contests still in play.

Two of the six, Colorado and Nevada, look like tossups. But in a year like this, the party with a strong wind at its back normally has a better-than-even chance of winning the jump balls. In Colorado, in particular, Ken Buck (R) appears to have a slight advantage over Sen. Michael Bennet (D). The Nevada race is so tight, and both Sen. Harry Reid (D) and Sharron Angle (R) are so unpopular, that any outcome is possible.

If Democrats lose both tossups, Republicans would have a net gain of eight seats, and they would need two of the remaining four contests -- West Virginia, Washington, California and Connecticut -- to net 10 seats