There are 30 Democratic-held U.S. House districts up in 2020 that Donald Trump won in the 2016 presidential election. Incumbents have filed for re-election in 28 of the 30 districts. Most are expected to be among the House’s most competitive elections in 2020.

The 30 districts voted for Trump by as many as 30.8 percentage points (MN-07) and as few as 0.7 percentage points (IL-17). In 2012, 16 voted for Mitt Romney and 14 voted for Barack Obama.

In 2018, there were 13 Democratic-held U.S. House districts up for election that Trump won in 2016. Three of the districts flipped, electing a Republican representative in 2018. After the 2018 midterm elections, 31 districts that Trump won in 2016 were held by a Democrat.

In December 2019, Jeff Van Drew of New Jersey’s 2nd Congressional District announced that he was switching his affiliation from Democratic to Republican, bringing the number of Democratic-held U.S. House districts that Trump won in 2016 from 31 to 30.

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 Republican in 2020 and won by Hillary Clinton 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