There are five Republican-held U.S. House districts up in 2020 that Hillary Clinton won in the 2016 presidential election: New York’s 24th, North Carolina’s 2nd, North Carolina’s 6th, Pennsylvania’s 1st, and Texas’ 23rd.

The five districts voted for Clinton by as many as 24.4 percentage points (NC-02) and as few as 2.0 percentage points (PA-01). In 2012, one district voted for Mitt Romney (TX-23), and the other four districts voted for Barack Obama.

Two incumbents in these districts are seeking re-election: John Katko (NY-24) and Brian Fitzpatrick (PA-01).

The redrawing of North Carolina’s congressional districts in 2019 increased the number of districts won by Clinton in 2016 and held by Republicans in 2020 by two. Prior to the redistricting, no district with a Republican incumbent voted for Clinton. After the redistricting, two districts that closely resembled an old district with a Republican incumbent voted for Clinton: the new 2nd (George Holding) and the new 6th (Mark Walker). Neither Holding nor Walker filed to run for re-election in 2020.

In 2018, 25 Republican-held U.S. House districts that Clinton won in 2016 were up for election. Incumbents did not seek re-election in eight of the 25 districts. Twenty-two of the Republican-held districts flipped and elected a Democrat in 2018.

From 1900 to 2016, the percentage of congressional districts that voted for a presidential candidate of one party and a U.S. representative from a different party ranged from 1.6 percent (five districts) in 1904 to 44.1 percent (192 districts) in 1972. The 2016 election had the sixth fewest split districts since 1904 with 8.0 percent (35 total).

Additional reading:
U.S. House districts represented by a Democrat in 2020 and won by Donald Trump in 2016
U.S. House districts won by Hillary Clinton and a republican in 2016
U.S. House districts won by Donald Trump and a Democrat in 2016