The race to be the next U.S. representative in the Eighth Congressional District is close, very close. And pundits say voter turnout will play a key role in who wins the competitive open House seat.

Democrat Kim Schrier has taken a razor-thin lead over Republican Dino Rossi in the latest polls.

A New York Times/Siena College poll, conducted between October 30 and November 4, Schrier led Rossi by 3 percentage points. Monday’s Cook Political Report, a nonpartisan newsletter analyzing elections, also changed its rating of the race from a "toss-up" to "lean Democratic."

But it's still too early to tell, with a large chunk of undecided voters who could turn the tide one way or another. What will ultimately decide the race, pundits say, is which party will be more successful in drawing out their voters.

“Trump has worked really hard activating voters who don’t typically vote,” said David Wilkerson, University of Washington political science professor. “The question for Democrats is, can they get young people to turn out?”

Both locally and nationwide, early and absentee votes are already showing spikes in turnout compared to the last midterm’s historical low. For the slight edge, Republicans generally target less educated white voters; Democrats set their sights on the youth vote.

Compared to the last midterm election, national voter participation among those who didn't go to college—an education level of high school graduation or less—is up by 84 percent. Participation among people ages 18-29 rose by 123 percent, according to TargetSmart analytics.

Mark Smith, associate chair of University of Washington's Political Science Department, said he thinks Schrier could take the seat based not on a single demographic, but on overall party turnout. In the August primary election, Democrats had a larger turnout than Republicans.

“Assuming that she can consolidate the results,” Smith said, “my suspicion is that she’ll end up winning by a few percentage points. I think it’ll go to Schrier.”

The Eighth Congressional District—spanning areas both east and west of the Cascades, including Ellensburg and eastern parts of King and Pierce counties—has been a Republican stronghold for decades. U.S. representative Dave Reichert's announcement that he would retire left the seat vulnerable to a Democratic takeover.

Both candidates together have drawn $28.2 million in total contributions, including $18.9 million in outside spending. That makes the Eighth District the most expensive House race in the country, according to OpenSecrets.org.