I've been hearing about the changing demographics for 20-30 years now. I don't think it has had that much of an effect. What I keep track of is party affiliation which includes all demographics. Puts them into three groups, Republicans, democrats, independents. Those three groups include every demographic.

For this election party affiliation was at 31% Democrat, 29% Republican, 40% independents. Average party affiliation by decade.
1950 - 45% Democrat, 31% Republican, 18% independent
1960 - 46% Democrat, 29% republican, 23% independent
1970 - 46% Democrat, 23% Republican, 29% independent
1980 - 39% Democrat, 29% Republican, 29% independent
1990 - 35% Democrat, 27% Republican, 33% independent
2000 - 33% Democrat, 25% Republican, 35% independent
2010 - 33% Democrat, 25% Republican, 37% independent
2020 or today - 31% Democratic, 29% Republican, 40% independent.

The trend, the GOP has remained in the high 20's for 70 years, the Democrats have been steadily shrinking and independents rising. This despite the demographics. If those who affiliate with the Democratic Party start rising, then I'll believe demographics are beginning to make a difference.

Demographics the difference between the presidency and house election. Those voting for Trump and those voting for Republican congressional candidates

White 57% for Trump, 59% for Republican congressional candidates
Blacks 12% for Trump, 12% for republican congressional candidates
Hispanics 32% for Trump, 36% for Republican congressional candidates
Asian 32% for Trump, 34% for Republican congressional candidates.

There are the ticket splitters broken down via demographics. Via party ID
Democrats 94% Biden, 95% Democratic congressional candidates
Republicans 94% Trump, 94% Republican congressional candidates
Independents 54-41 Biden over Trump, 52-46 Democratic congressional candidates over Republican congressional candidates.

Independents are your ticket splitters which caused the GOP to gain house seats. Considering the Democrats had 236 to defend vs 198 for the republicans.

The above figures aren't the final figures as the vote counting continues. But they're close, no more than a one point change one way or the other is expected to change.

It's high past time that we start electing Americans to congress and the presidency who put America first instead of their political party. For way too long we have been electing Republicans and Democrats who happen to be Americans instead of Americans who happen to be Republicans and Democrats.