Nearly 18 percent of Virginia voters remain undecided ahead of Tuesday's Virginia gubernatorial debate between Democrat Ralph Northam and Republican Ed Gillespie.

A new Fox News poll gives Northam a slight edge over Gillespie, 42 to 38 percent, Northam's advantage is within the survey's four-point margin of error.

The two are set to square-off Tuesday evening at George Mason University with the latest poll showing many Virginia voters could still change their mind.

Just over a quarter of voters, 27 percent according to the Fox poll, indicated they could vote for another candidate come Nov. 7.

Both campaigns have spent heavily on television advertisements, particularly in voter-rich Northern Virginia. Advertisements from Northam, who is the state's lieutenant governor, have sought to paint Gillespie, a political consultant and former chairman of the Republican National Committee, as a Washington insider who caters to lobbyists. Gillespie's ads have accused Northam of supporting sanctuary cities.