I think Democrats are favorites to win 1980 simply because Republicans will have held office for 12 years, and voters would be ready to give the other party a chance. When you add in stagflation, it makes that outcome even more likely. I'll leave the others to go into more detail about the Presidential race, but I'd like to focus on what a Ford Presidency means for Senate elections in 1978 and 1980, because this will have a huge impact on what a possible Democratic President after 1980 would be able to accomplish.
With a President Ford during the 1978 midterms, you can expect a shift in voting percentages away from Republicans and toward the Democrats compared to what they were in President Carter's midterm, as people tend to vote against the party in control of the Presidency. I think Democrats still lose Colorado, Maine, and Mississippi, because those elections were blowouts in the OTL so a shift of a few percentage points would not change anything. They might still lose South Dakota, especially if Senator Abourezk retires. He only served one term and was just 47 years old at the time, so I'm not sure if his decision was based on a tough re-election fight in a bad midterm situation, or if he was really just tired of politics. Since I don't know what his intentions were and what the numbers of a matchup between him and Pressler would be, I'll say he still retires and Pressler wins the seat. So that's 4 pickups for Republicans.
For the Democrats in 1978, I'd say they still pickup Massachusetts, Michigan, Nebraska, New Jersey, and Oklahoma as in the OTL. Texas and Virginia were both decided by a half a percent or less, so with a national swing of a few points those should be pickups for the Dems too. Illinois, New Mexico, and North Carolina would be much closer, giving the Democrats a chance to win some of those seats. I think Helms survives in North Carolina, but Democrats win Illinois and New Mexico. So that's 9 possible pickups for the Democrats.
Without Mondale becoming VP the clusterfuck in Minnesota doesn't occur, with Governor Anderson resigning office to take the seat and new Governor Perpich being involved and both of them losing their elections in the midterms. Now Mondale stays in office and should win re-election in 1978. Humphrey still dies, and his wife is still appointed to fill the office until the special election in 1978. But now Anderson can run for that seat while finishing up his second term as Governor, and Perpich will run for Governor and both probably win in this timeline. Then there are some of the close races Democratic incumbents lost that could switch in this timeline. A shift of just a couple of points from Republican to Democrat should save Dick Clark in Iowa, and McIntyre in New Hampshire.
So after the 1978 midterms we have 9 Democratic pickups to 4 Republican, giving Democrats a net gain of 5 seats, to bring their numbers up to 66 seats in the Senate, while Republicans have 33, and Harry F. Byrd, Jr. of Virginia as the lone Independent who caucuses with the Dems.
The 1980 Senate races will have even bigger changes without the Reagan wave to bring in 12 new Republican Senators. Even if Reagan runs in this timeline and gets the nomination, the conditions will not be there for a Republican wave election. If anything the momentum would be with the Democrats after 12 years of Republican Presidents. Democrats would be defending a bunch of the seats held by the Watergate Babies, so there aren't too many pickup opportunities. The only possible close races of Republican controlled seats are in Arizona, New York, Oklahoma, Oregon, and Pennsylvania. Goldwater held his seat by just 1.1% in a Republican wave year, so he's toast. Al D'Amato defeated Elizabeth Holtzman in New York by just 1.4%, so he will lose too, and Holtzman becomes the first Female Senator from New York instead of Hillary Clinton 20 years later. I think Don Nickles still holds Oklahoma for the Republicans in this timeline. He won by 10% in the OTL, and even though it is much closer this time, that's a big gap to make up. Packwood probably wins re-election in Oregon in a squeaker, so another Republican hold. In Pennsylvania, Specter won the seat of retiring Schweiker by just 2% in the OTL. If Schweiker still retires then Flaherty probably beats Specter. So we have 3 likely pickups for the Democrats in 1980.
As for possible Democratic holds, there are 6 seats that Republicans won by less than 3.5%, so I say they definitely stay Dem this year. Those are Alabama, Florida, Georgia, Idaho, North Carolina, and Wisconsin. Another 5 were won by less than 8.4%, so when you take out the wave those become much closer. I think Democrats could hold all of those as well if this becomes a Democratic wave election. The only seat Democrats will probably lose is McGoverns in South Dakota, which was lost by 18.8% in the OTL. So we have a possible Republican pickup of 1 seat.
That means the Democrats win 3 to the Republicans 1, for a net gain of 2 seats, bringing their numbers up to 68 Senate seats, against 31 Republicans, and Independent Harry F. Byrd, Jr. of Virgina who caucuses with the Democrats. With 68/69 votes in the Senate as well as even bigger control of the House, and the Presidency, the Democrats could pass a lot of their agenda in 1981-1982.
