It sounds like Reagan won by a much narrower margin than historically in 1980. He may not enjoy as thick a layer of strength and superiority over his opposition as in OTL.
Historically, that was an R+10 presidential election; in this timeline it was R+4. If the distribution of votes were the same, that means that his opponent (Carter, or was someone else the (D) incumbent, or what, I forget) would have picked up most or all of the following states that historically flipped Reagan:
Massachusetts
Tennessee
Arkansas
Alaska
Mississippi
Kentucky
South Carolina
North Carolina
Delaware
New York
Maine
Wisconsin
Possibly Louisiana, Vermont,
maybe Michigan, probably not Missouri or Pennsylvania.
So we're looking at an election that was much less of a blowout for the Gipper.
...
And yes, that is a list of
purple states in the 1980 election. The ones that were close but voted Reagan. If this trend continues to other 1980 elections, the Democrats are likely to maintain their supermajority in the House of Representatives (they managed it in OTL anyway), and the Republicans probably didn't pick up twelve Senate seats to get themselves a 53-46-1 majority.
In fact, the Republicans had
ten Senate races that were decided by a margin of 5% or less, so if Reagan underperformed OTL by six points (R+10 to R+4), and if his coattail effect was correspondingly weakened...
The Republicans probably don't have a Senate majority at all TTL. They'd have failed to flip about seven seats, and potentially lost about three seats to the Democrats, and the Democrats would have somewhere in the neighborhood of 55 seats.
So Reagan may be sitting alone and facing an entirely Democratic legislature.