I predict the Democrats will take the Senate, holding 51 Senate seats when the new Congress convenes on 1/3/2021.
I predict the Democrats will lose a seat in Alabama and win GOP held seats in Arizona, Colorado, Maine, North Carolina and Iowa. I predict Lindsey Graham will be reelected in South Carolina for the GOP by a tiny margin, perhaps in a recount. I predict the GOP will eventually hold both Senate seats up for election in Georgia (though the Democrats COULD win 1 or even both on a BIG Biden blowout win). There are other Democrat opportunities for pickups, notably Montana, but absent a Biden win by more than 10 points nationally I don't expect any of these to come to fruition. Finally, the GOP has 1 other longshot pickup opportunity in Michigan. I expect the Dem to win by about 5 points, not a sterling performance, but enough to keep his seat.
The Democrats currently have 47 seats (counting the two "independents" that caucus with the democrats, Bernie Sanders and Angus King of Maine). Assuming Biden wins the election (as I strongly predicted in my previous post), the democrats need 50 Senators to control the Senate (with newly elected Vice President Kamala Harris breaking the tie). Doug Jones of Alabama will lose. Yes the polls are close. Yes he will do much better than Biden in Alabama. But Alabama is too red to elect a democrat unless, say, a child molester running against him. So the Democrats will "start" with 46 seats and need 4 to take control (again assuming Biden wins).
Prediction: Democrat Mark Kelly by 8.
Fundamentally, Arizona should be a Biden state (but not by much at all!), and the democrat should run well ahead of Biden. Easy democratic pickup. Predict the democrat wins by 8.
In Arizona, Nate Silver's model, at https://projects.fivethirtyeight.com/2020-election-forecast/senate/ predicts the Arizona Senate vote will be 52.8-47.2, or the democrat, Mark Kelly, by 5.6 points. I would definitely take the over on that. Biden will likely (but not definitely) win Arizona, the state hasn't warmed to incumbent Republican Martha McSally, and Kelly is a GREAT candidate (former astronaut and husband of former Congresswoman Gabrielle Giffords, who was shot in the head at point blank range some years ago and survived.
Prediction: Democrat John Hickenlooper by 9
Colorado will be an easy pickup for the Democrats. CO is a blue state at this point; I have Biden winning it by 12.5 (Nate Silver has CO going for Biden by an expected 11.5 points). Voters rarely split tickets these days. The Colorado Senator is linked to Trump. The democrats are running a mildly popular former governor. John Hickenlooper is not a natural politician, but he's acceptable. Nate Silver's model has Hickenlooper predicted to win by 7.6 points. I would again take the over, but not by much. I used to think Hickenlooper would outrun Biden; I'm not so sure of that now. But it won't matter.
Prediction: Democrat Sara Gideon by 6
Susan Collins, aka Concerned Susan for Democrats that follow this stuff closely, will lose. She used to have a LOT of crossover appeal, with Democrats voting for her in significant numbers in past elections. Not this time. Nate's model has her losing by 2.6 points to Sara Gideon, the state House Speaker. I would yet again take the over, as I expect Gideon to win by about 6.
If I only expect a 6 point win how can I be so very confident? A very fair question. Especially since Maine is an elastic state (meaning it has relatively more voters than average that will change their minds). It would take a while to explain, but the short version is that Gideon is up in virtually every poll and more importantly Biden will win Maine big. Hillary C only won Maine by 3, whereas I have Biden winning it by 12! Collins will outperform Trump for sure in this light blue state, but not by enough to make up a 12 point stagger.
Prediction: Democrat Cal Cunningham by 3
If the 3 above races go as I predict, North Carolina would be the 4th seat that Democrats would need to take the Senate. I predict that the Democrats will win this seat, although we reach the first seat where I'm not super sure. I have Biden winning North Carolina by 1. While I'd way rather be Biden than Trump in NC, I'm obviously not sure about Biden winning it. Democrat Cunningham should outrun Biden. This was a near certainty until Cunningham became embroiled in a sexting scandal. Most important Senate race for determining Senate control (the most likely Senate tipping point if you will) and the GOP candidate gets COVID and the Democrat has a sexting scandal. So 2020.
Anyway, we should know the winner of NC, and this seat, on election night, unless one or both are VERY close, as NC will have its ballots counted very quickly (as will Florida).
Prediction: Democrat Theresa Greenfield by 1
I have Trump winning Iowa by about 1. I do expect Greenfield to outrun Biden, but NOT by much. So while I am predicting Greenfield to win, the real answer is: (1) I don't know who is going to win this race; and (2) you don't know either. How Biden does nationally will likely decide this race. If Biden wins in a blowout, by say 10 points nationally, the Republican, Joni Earnst, is toast. If Biden wins by only 6, I would predict that Ernst survives and holds the seat for the GOP. At my 8 point prediction this race is close but SLIGHTLY favors the democrat. I note that Nate Silver's model forecasts the election as a 1 point win for the Democrats. So I'm basically cheating. Don't tell anyone please.
Prediction: GOP Senator Perdue by about 1.5 points.
Prediction 2: The other seat is CERTAIN to go to a runoff election IN JANUARY, likely with 1 Democrat and 1 Republican. I think the Democrat will be a modest underdog, though I am very uncertain about that. Usually Democrats lose runoffs, but if the Biden rout that I predict does come to pass, there is a real chance of a dispirited GOP base in Georgia simply not bothering to show up for a runoff while a still enthused Democrat base does.
I have Biden winning Georgia by 0.8 points. Wouldn't be surprised by 3 points either way on that prediction. Crucially, Perdue is VERY likely to outrun Trump. Hence my prediction that he hangs on. But on a big Biden night, Perdue could well lose. The problem Democrats have here is that it is Trump that is causing Georgia to be so close. There is no objection to Perdue that I am aware of among the state GOP and right leaning independents. Hence he outruns Trump. Hence he probably holds on.