Here are the changes from last week.
Probability of Republicans holding the Senate outright: 53.8%, up from 43.8%
Probability of a 50-50 split: 29.2%, down from 30.7%
Probability of the Democrats taking the Senate back: 18.0%, down from 25.5%
My algorithm currently is set up to follow ten close races. As of this week, there are only four I consider truly close and the Republicans are playing defense in all of them.
Probable Republican pick-up: Harry Reid is retiring and Republican Joe Heck has held a consistent slim lead in the polls for months now in the race to replace Reid.
Very likely Republican losses: Russ Feingold in Wisconsin and Tammy Duckworth in Illinois are strong favorites to gain two seats for the Democrats. This would mean a net gain of one for the Democrats and the GOP would still have 53 senators.
Very likely holds for both parties: There's currently very little drama in Missouri or Florida for the Republican incumbents and even less drama in Colorado for the Democratic incumbent.
The four close races:
Indiana: Very little polling here and the most recent poll has Evan Bayh with a very slender one point lead, down from four in September and seven in August. My system now puts him as a 61% to 39% favorite, down from 85% to 15% just last month.
Pennsylvania, New Hampshire and North Carolina: Many senate races have been polled only sporadically, but that is not true in these three states. In all three cases, there have been recent polls in favor of the Republican incumbents and others in favor of the Democratic challengers. Both Pennsylvania and North Carolina are flat-footed ties in my system and Kelly Ayotte's advantage in New Hampshire is about 51% to 49%. All three of these states are now in the Leaning Clinton camp. So far, the coattails on Hillary's pantsuits have been literally and figuratively very short.
Back tomorrow with news on the presidential race. Spoiler alert: all the competent aggregators agree on the general trend, though there is disagreement on the current odds.