Since the middle of September, the conventional wisdom here (and at other sites like 538) has been that, yes, Republicans have a slight edge when it comes to the possibility of control of the Senate, but they are not heavy favorites and the Democrats don't need to panic.
That's probably changed now. Republicans now have a 73.3% chance at winning an outright majority, up from 69.8% yesterday. It's at a tipping point now where the GOP has about a 3 to 1 chance of winning Tuesday night.
The balance of the Senate is almost assuredly going to rest on three states: Iowa, Kansas, and Georgia, with Alaska as a wild card. Democrats would need to win three of those four contests, assuming they kept other states in which they are ahead (NC and NH) and lost the other states in which they have consistently trailed (CO, AR, LA, KY, WV, SD, and MT). That scenario would also include the Kansas Independent caucusing with the Democrats, as we assume.
Overall, the races in all of those four states are pretty close, with Alaska being a bit more of an unknown. We had a flurry of polling out of Iowa yesterday showing a statistically tied race. However, yesterday the Des Moines Register poll found Ernst leading by seven points. The Register poll is typically an excellent bell-weather for where the state is at. However, it's extremely unlikely that her lead is seven points, when every other poll has shown something between a two point lead for her to a one point lead for Braley. Still, Ernst's chances of winning have risen to 63%.
Kansas is now ranked as the closest state in our forecast. Each side has an exactly 50% chance of winning. Orman has had a slight lead in most recent polls, but the conservative tilt of the state will likely help Roberts with undecided voters. Democrats need Orman to win and then decide to caucus with them.
In Georgia, it now seems as though neither side will win on Tuesday. Most polls show the race as tied or giving it slightly to Perdue. But Perdue isn't getting to 50%, mainly due to the Libertarian on the ballot. At this point, Democrats should be happy if the race goes to a runoff. That won't necessarily give Democrats more of an advantage, but it gives them a longer time to get ahead again in the polls. Currently, Perdue has a 60% chance of eventually winning.
Finally, Alaska is our wild card. As we discussed this week, polling in Alaska is scarce and unreliable. We have a couple polls now showing the Democratic incumbent with a large lead and multiple surveys showing the Republican, Dan Sullivan, with a marginal lead. To make it even more suspenseful, we likely won't know the final tally of the votes in Alaska for a week or two after the election.
It all ads up to the likelihood that we won't know the fate of the Senate on election night, unless Republicans pull off surprise wins in places like North Carolina and New Hampshire. If that happens, Democrats are going to have a long night, and it will be apparent that the polls were skewed towards the Democrats the entire time. However, the opposite could happen; if Democrats win by larger than expected margins in those east coast states, it may be a sign that the polls were biased towards the Republicans.