Chris Krueger, managing director of Cowen & Co.’s Washington Research Group, said he sees four “glaring red flags for the House GOP majority”:

The correlation between the president’s approval number and first-term midterm losses by the president’s party: In the six times that the president’s job approval was under 50%, the average loss was more than 43 seats. The Democrats need 24 to flip the House.

CA + PA = half-way there: California is the citadel of the resistance, which has 14 House Republicans. Between retirements, losing state-and-local tax deductions in the tax bill, and Trump’s California disapproval, the Golden State could lose half its GOP delegation. The new Pennsylvania redistricting map — and similar anti-Trump trend lines — could cost Rs as many as six seats. These two states get you halfway to a Democratic House.

Suburban danger zones: 2018 could make the suburbs great again for the House Democrats. The Democratic victories in last year’s Virginia and New Jersey governor’s races could well be the canaries in the coal mine. Remember that there are 23 House Republican seats in districts Clinton won — and most are suburban.

Trump Coalition Unique to Trump: This is the biggest wildcard.