Why Democrats have a shot in a Georgia district dominated by Republicans

But Mr. Trump’s weak performance last November was a sign that this race could be competitive.

In congressional elections since 2004 without an incumbent, the results of the previous two presidential elections have been much more important than the results of the last congressional election in predicting the results of a race.

Moreover, the most recent presidential election has been more important than the preceding one — a warning sign for the Republicans in a district where Mr. Romney did well but Mr. Trump did relatively poorly.

Mr. Price’s 62 percent of the vote in November was not an indicator that this was a safely Republican district. There are plenty of Republicans who do as well while representing competitive or even Democratic-leaning districts. My hometown representative, Dave Reichert, a Republican in Washington State, won 60 percent in a district won by both Hillary Clinton and Barack Obama. There are many other examples.