With 14 months to go before Election Day, the House battleground continues to take shape. Even though there is some uncertainty about what the political climate will look like next fall and whether normal historical midterm trends will hold under President Donald Trump, the House playing field is expanding, almost entirely in the Democrats’ direction.

As we’ve mentioned plenty of times before (and will likely repeat over and over again), history puts the Republican Party at a disadvantage: The president’s party has lost seats in 18 of the last 20 midterm elections, with an average loss of 33 seats. Democrats need to gain 24 seats next year for a majority.

Midterm elections often a referendum on the president, and when voters disapprove of his performance, they punish his party because his name isn’t on the ballot. Historical trends are based on that dynamic.

But what happens when voters perceive the president to be outside the traditional two-party system? Trump is technically a Republican because he ascended through the GOP nominating process. Still, many voters see him as his own brand rather than as a party leader. If that differentiation continues, GOP candidates could avoid the typical midterm disaster.