The House is, for all that every member is up for re-election every two years, not likely to flip to Democratic control any sooner than 2022, and probably not even then. The reason is simple, the party in power gets to stack the deck every time the census comes around. Gerrymandering doesn’t have to happen, the politicians do it that way to prevent random cases of democracy breaking out.
But there is no way to gerrymander the senate. Each state gets two senators, and they are elected at large. There is not way to rig the game to make sure one side isn’t given a fair chance to win.
The clearest example I know of is California.
California is, by the numbers, a fairly blue state. 2/3rds of her voters voted for Obama. What does her House delegation look like? These days it’s pretty close to those numbers; prior to the passage of Prop. 20, in 2008, that wasn’t the case.
What does that mean for the next president (who needs to have some support, somewhere, if anything productive is going to happen)? That, as they say, depends. Incumbency is a pretty powerful thing. Lots of people say “turn the bums out”, but when pressed think their bum is ok. I remember, some years back, being at a party. It was a party full of Quakers. Of liberal Quakers. Liberal Quakers who had David Dreier as their Representative.
The host of the party, a moderately liberal Quaker, had a David Dreier yard sign, in 2002. When asked why he said, “He’s done good things for Monrovia”. That’s the power of incumbency.
But, lots of states have so gerrymandered their House districts that the Senate is at greater risk. Looking at the House Delegations (and remembering incumbency) seats look safer than they are. But years of being disenfrachised, on the one hand, and the present level of disarray in the Republican Party had already put some Senate seats in moderate play.
Then Scalia died. The level of obdurate, obviously partisan, obstructionism the Senate got a huge spotlight. The Senate, you see is supposed to be above that sort of thing (not that they have been for, at least 20 years) but before this they could appeal to the “Senate’s tradition of bipartisanship” and folks would believe it. The real problem is there was a bout of this a few years ago, which was resolved with the “Gang of 14” who were supposed to see to it that, so long as no “extreme” judges were nominated, there would be “up or down votes” on nominees.
That failed. It very quickly became obvious that the definition of “Extreme” was anything to the left of Roberts.
But the public could ignore than when it was Federal judges being stymied. The crises at the district (and circuit) levels isn’t that visible to most people. The one time they pay attention to the recommendations of the Senate Judicial Committees is when there is a Supreme Court nominee.
Which couldn’t have come at a worse time for the Republican Party.
Because the question of who gets to appoint justices to the Supreme Court is usually theoretical. It’s something policy wonks worry about, but most people don’t watch the court closely enough to consider it. They see nominations as random. They don’t look at actuarial tables and wonder who is likely to die. This year it’s right there, in the open. And those blue states with Red Senators… suddenly have a big reminder of how much their vote matters.