The Democrats are likely to lose the senate for two years. My predictions have been consistently more bullish on Republican victory than any of the other main forecasters: New York Times’ Upshot, FiveThirtyEight, HuffingtonPost’s Pollster, Princeton’s Sam Wang, etc. And, to be frank, the data is more generous to the Democrats than my gut, but I am obliged to run with the data.
The Democrats will have 47 seats if they take all of their certain races, along with New Hampshire and North Carolina. Of course, New Hampshire and North Carolina are not certain, but for the sake of this exercise, let us assume the Democrats take those seats. There are just eight other seats that are even remotely in play, and the Democrats would have to win three of them to get to a 50/50 tie, where Joe Biden is the tie-breaker.
Three of the races are extreme longshots: Arkansas, Kentucky, and Louisiana. In both Arkansas and Kentucky the Republican has been consistently leading by more than 5 percentage points. Neither of these states are particularly susceptible to polling error, they do not have fast moving populations, high levels of Hispanics, etc. So, it is unlikely they will suffer a catastrophic poling failure. In Louisiana Landrieu is within striking distance, but is hurt by the majority voting system. Senator Landrieu will not get 50% of the vote in the original vote and Democrats tend to suffer in runoffs, because Democratic voters are less likely than Republicans to bother voting twice. Winning any of these three elections is become extremely unlikely.
The Democrats really need to get three of the five other races, but they all pose their particular problems. First, Colorado is drifting back to the incumbent Democratic governor and, to be frank, the senatorial polling is a bit of mystery. The Democratic incumbent is liked and the state is reasonably blue. Despite consistent polling showing Udall losing, Colorado is a state that polling error is possible and early voting is confusing. Second, Iowa, like Colorado, is one that I would have expected the Democrats to challenge closer, but the polling is consistent for the Republican. This state is a little less blue than Colorado, less likely polling error, but the Democratic candidate has been closer all race. Third, Alaska is Republican state and the incumbent Democratic senator is polling consistently behind. He would not be in this race at all except for two crazy outlier polls showing him dominating. Fourth, Georgia shows the Republican in the lead and, again, the Democrats are not poised to do well in a possible runoff. Finally, the race in Kansas is a toss-up, but with the Republican governor almost definitely going to lose, expect people to split their vote in the ballot box and keep the Republican senator.
Actually, the Democrats really need to get three of the four race that are not Kansas. I doubt an independent Senator Orman will cast the deciding vote in the senate for the Democrats, because that would be political suicide for him in 2020. Instead, if the senate is 49 Democrats and 50 Republican, expect Orman to caucus with the Republicans in 2015-6 and then he will quietly caucus with the Democratic majority that will take over the senate on January 1, 2017.
All of this begs the question, can the Democrats capture Iowa, Colorado, and either Georgia or Alaska. It is possible, but if Sam Wang or Nate Silver were backing up their probabilities with real-money bets. To translate, Sam Wang is implicitly saying he is good getting $60 if the Democrats control the senate and paying me $40 if not, while Nate Silver is implicitly saying he is good getting $70 if the Democrats control the senate and paying me $30 if not. I consider a fair wager at $80 if the Democrats control the senate and $20 if not.
Here is New York Times and FiveThirtyEight compared with PredictWise. The one key difference is the other forecasters are much more bullish on the Democratic pickup in Georgia. I admit one key issue is that there is no historical identification for what will happen in a runoff that determines the balance of power in the U.S. Senate.