Having had 4 hours of sleep on this, I'm going to go even farther then I did last night. I would suggest that vote totals for Congress are essentially irrelevant in driving party behavior.
There may be dozens, hundreds, or thousands of reasons for this, and I'm a lawyer, not a political scientist. However, from my view, it would appear the primary motivator for changes in partisan behavior is presidential election results.
Democrats lost the 1968, 1972, 1980, 1984, and 1988 races with an ambiguous win in 1976, before deciding that their presidential candidate must be facially moderate.
Republicans lost in 1992, 1996, 2008, and 2012 elections, with only one of their two wins in the interim decided with a majority of the so-called popular vote.
The candidates with whom they lost those elections, including in one case an incumbent President, were largely indistinguishable in broad strokes of policy and temperament.
At the same time they were losing those presidential elections, they were winning Congress for the first time in decades, holding it, losing it briefly, and then regaining it in landslides.
The change in the nature of their presidential nominee did not occur until they had been repeatedly whipped at the presidential level.
Again, I am not a political scientist. However, these data are strongly suggestive of the idea that Americans believe the most important political marker is success in presidential elections.
That in turn suggests that the most important thing one can do, if the goal is to remove Donald Trump's influence on the Republican Party, is to make sure Donald Trump loses his reelection bid.
Anything other than that is it best a waste of time.
