The 2020 Senate contests will have the same effect. All but two of the Democrats up for reelection are from states that Hillary Clinton won in 2016, meaning they are more likely to lean on their base than seek out independents or Republicans. And because all but two of the Republicans are from states that Trump won, they are less likely to do anything that can be considered a break from the White House and risk a tweet from Trump.

Source: Los Angeles Times January 31, 2019 10:52 UTC