Fully 39 percent of registered voters say they would support the GOP candidate for Congress in their district, while 38 percent would back the Democratic candidate. Nearly a quarter of voters, 23 percent, are undecided.

Voters are split almost evenly along party lines. Democratic voters break for their party, 85 percent to 5 percent, while Republicans similarly favor the GOP, 84 percent to 8 percent. Among independent voters, 26 percent would vote for the Democrat, 25 percent for the Republican and nearly half, 49 percent, are undecided.

The GOP’s 1-point advantage comes after three months of tracking in which Democrats maintained a lead ranging between 2 and 10 points on the generic ballot.