►The numbers. Due to gerrymandering, Democrats need to win the nation popular vote by up to 11 percentage points to secure a House majority, a Brennan Center report found. That’s more than five times Hillary Clinton’s 2.1-point popular vote advantage in 2016. Could Democrats win by a margin of 9.4 points and not take control of the House? That’s exactly what happened with Virginia’s House of Delegates last November.

►The base. The Republican base has shown up in every off year election since 2010; Democrats have not. So much depends on voters who haven’t cast a vote in an off-year election in 12 years, or ever. And the Supreme Court continues to wither away voting rights, sharpening the powerful tool of voter purges in the right’s already potent voter suppression arsenal.

►The money. After years of making it easier for anonymous donors to spend unlimited amounts of cash electing candidates, the Supreme Court has quietly put public sector unions, the largest institutional supporter of the Democratic Party, on life support. And while the tax cuts don’t seem to be swaying many voters, big donors made big promises to get them passed. And you can expect to see at least a fraction of the billions the Republican Party sent their way raining down on endangered Republicans.