Democrats have been making the argument that the American voter was going to punish Republicans for the last four cycles, 2010, 2012, 2014, and 2016. They were going punish Republicans for obstructing President Obama's agenda. They were going to punish Republicans for the government shutdown. They were going to punish Republicans for blocking President Obama's Supreme Court nominee. There was a long list of things the voters were supposed to punish Republicans for. They never did. Republicans won the House vote by 7% in 2010, lost it by 1% in 2012, and won it by 6% in 2014, and 1% in 2016. Every time in the past Democrats claimed Republicans would be punished they weren't punished. So why would they be right now?
There's one big reason. There's a Republican in the White House, not a Democrat. Yes, voters have punished congress a few times before, but the President's party almost always gets beat in a mid-term. A President galvanizes the opposition in a way nothing else can. And Democrats are showing a lot of opposition. It's true that the mid-term electorate has favored the GOP in the past but that should be seen as immutable as the Permanent Democratic Majority was.
Less people always show up in a mid-term. In seven mid-terms from 1986 to 2010, the electorate was 71-76% of the previous Presidential electorate. In 2014, it was 64%. Both sides will lose voters who don't see it important to vote in a mid-term. If Democrats lose 20% of their voters and Republicans lose 30% of theirs, Democrats win the House vote by 8% in 2018. And that's certainly possible. While Democrats have had more voters indifferent about the mid-terms in the past they might not be indifferent with Donald Trump in the White House. Well, at least enough less of them might to help Democrats win.
There's another factor which often hurts the party in the White House. Swing voters are often disappointed. They expect something and the President doesn't deliver. The good news for Republicans is that Trump voters don't regret voting for him. Yet. There's still time.
In 2016 Donald Trump wasn't closely associated with House and Senate Republicans. There were many Republican held districts where Trump dropped off heavily from Romney and the House Republican didn't really drop off from how they did in 2012. The reverse was true. House Republicans failed to make inroads in many districts where Trump did a lot better than Romney. That was seen as unusual in age the experts insist there isn't ticket splitting. Of course, that was when Trump wasn't in office. It's a lot easier to see Republicans in the House being associated with Donald Trump now that they're working together. That could be a double edged sword. Yes, Republicans in Clinton won districts could suffer but Republican challengers in districts Trump won could take those. There's a lot of talk about 22 Republican districts Clinton won but not about the 11 Democratic districts Trump won. If Republicans can take 1 Democratic district for every 2 they lose, they'll have a bad night but still keep the House.
Will the AHCA hurt Republicans? I actually don't think so. I think the opposition would be robust whether they passed this bill or they didn't. I don't think vulnerable Republicans who voted no will be spared. Democrats were already energized before this bill passed. I doubt that'd dissipate if they didn't pass it. I think Democrats should do very well in the 2018 election. Of course, others have predicted they'd do well in previous elections and that didn't really happen.