This Should Solve All Of Your Problems
By 
Donald Trump is a terrible candidate and is losing very badly. Showing at least some recognition of his cratering poll numbers, he has tried another campaign shake-up. It involves promoting a Breitbart executive and the theory behind it is that Trump’s campaign so far has been too sober and disciplined. What could possibly go wrong?
If you are a liberal and are not Thomas Frank, you will recognize this as excellent news, because the bigger Trump loses the better. We are already starting to get into territory where Trump could threaten the Republican House majority:
First, a very broad but important point from Blizzard’s tweets: It is VERY hard for a House candidate — whether incumbent or challenger — to run significantly ahead or behind the top of the ticket in a presidential year. The presidential race is so all-encompassing for voters — and House members/candidates typically so little known — that how the top of the ticket goes heavily dictates the results of House races. That’s true even in cases where the House incumbent specifically tries to run away from the top of the ticket; voters tend not to differentiate all that much — if they are voting against the Republican at the top of the ticket, they usually do the same down-ballot. It’s why political waves occur — and why we call them waves.
Now to the specific numbers behind Blizzard’s math. His calculation is that the best an endangered incumbent can hope for is to run five points ahead of Trump. So, how many Republican seats might that include?
The Cook Political Report lists 45 Republican seats and 11 Democratic ones as potentially competitive in November. Let’s focus in on those 45 Republican seats.
Of the 45, 40 remain largely intact from the 2011 national redistricting process. (Florida engaged in a mid-decade redraw.) For those 40 seats, we can overlay the Cook Report’s Partisan Voting Index (PVI) in an attempt to compare apples to apples. (The PVI ranks every district against every other district based on presidential performance.) Of the 40 GOP-held districts, 36 have a PVI of R+5 or lower, meaning that they are five points (or less) more Republican at the presidential level than all of the other districts in the country.
If Republicans lost all 36 of those seats with a PVI of R +5 or lower — and Democrats held all 11 of their contested seats — Democrats have the House majority. By six seats. Twenty-seven of those 40 seats have a PVI of R+3 or lower. Win those 27 and Democrats need to pick up only three seats among the slightly more Republican-friendly districts to win the majority.
One reason that the Democrats retain an outside chance of taking the House is that there’s a tipping point where gerrymandering works against the party that did it. Gerrymandering, by dispersing your supporters and concentrating the supporters of your opponents, gives you a substantial advantage in a normal election, but leaves you more vulnerable in the case of a wave. Trump being a historically bad candidate could be exactly that kind of tsunami. Trump’s decision to Be More Trump can’t hurt.