With 102 days to go, Democrats remain substantial favorites for House control. A big reason: Republicans are defending 42 open or vacant seats, a record since at least 1930. The retirements of Speaker Paul Ryan (WI-01), as well as powerful committee chairs like Reps. Ed Royce (CA-39) and Rodney Frelinghuysen (NJ-11) and popular moderates like Reps. Ileana Ros-Lehtinen (FL-27) and Frank LoBiondo (NJ-02), have given Democrats stellar pickup opportunities.

Of Republicans' 42 incumbent-less seats, eight are in districts that voted for Hillary Clinton in 2016, and an additional 13 are in districts where President Trump received less than 55 percent. History is working against the GOP in many of those seats: we found that since 1992, in situations when a president's party was stuck defending an open seat two years after the president failed to carry it, that party has batted zero for 23 keeping it in their column.

To NRCC Chair Rep. Steve Stivers's credit, only one additional Republican has retired since Ryan's announcement on April 11: Rep. Tom Garrett (VA-05), who in May said he would leave

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