Despite everything that's happened lately, as of last week, there were still more Republicans unhappy with their party in Congress than Democrats. 35% of GOP voters expressed disapproval of their leaders in Washington while 27% of Democrats did.
There's a big difference between the unhappy Democrats and the unhappy Republicans though. By a 77-12 margin the GOP voters mad at their party still plan to vote for it next year. The Democrats displeased with theirs only plan to support it by a 54-38 margin.
There's no doubt that disaffected Democrats are a bigger flight risk than disaffected Republicans, and a lot of Democratic members of Congress' actions seem to reflect that. The Democrats who say they might vote Republican next year are from the conservative wing of the party and so efforts are being made to placate them.
The question of course is how much those efforts will turn off voters in the much larger progressive wing of the party and cause them to stay home next year.
On an individual level it's more important to keep the conservative Democrats happy because if they vote Republican you're taking away a Democratic vote and adding a Republican vote whereas if you make a progressive Democrat mad and they don't vote you're just taking away the single Democratic vote. But if there are more than twice as many Democrats who stay home next year because they're disgusted with the party than there are voters who stay in the fold because the party didn't go too far to the left it's a net loss to the party.
Hard to know how to measure all that.