A growing number of voters say they plan to vote for Democratic candidates over Republicans exactly a year to the day before the November 2018 midterm elections.

Democrats hold an 11-point advantage in the generic congressional ballot, which does not name specific candidates but is considered a strong predictor of the results of upcoming elections, according to a new Washington Post/ABC News poll released Monday.

If the election were held today, 51 percent of registered voters say they would vote for a Democratic candidate over 40 percent who would cast their ballot for a Republican. That gap is the largest lead Democrats have held since October 2006, a month before midterm elections in which they won 31 seats in the House and six seats in the Senate, capturing majorities in both chambers, as well as six gubernatorial races.

Democrats traditionally hold a small advantage in the generic ballot, even in years when Republicans ultimately win more seats. As a result, analysts say they would need to do better than simply come out ahead, but instead would need to win between 5 and 8 points more votes in House races overall to overtake the Republicans' 45-seat majority in the House. Their path is even trickier in the Senate, where Republicans hold a 4-seat advantage, but are defending only 10 seats to the 24 Democratic seats up for grabs.

While the president's party has typically lost seats heading into its first midterm election, a spate of retirements is an indication many Republicans expect 2018 to be a particularly difficult year.

Despite President Donald Trump's historically low poll numbers, his unpopularity may not be behind Republicans' disadvantage in the generic ballot.

According to the Post-ABC poll, nearly half of voters – 47 percent – say Trump will not be a factor in their decision to vote for a Democrat or Republican for Congress. Meanwhile, 24 percent say their vote would be to show support of the president, while 27 percent say they would vote to show their opposition.