MADISON, Wis. -

Maryland Gov. Martin O'Malley said Wisconsin's recall election will be so close it could come down to two votes per precinct.

O'Malley, chairman of the Democratic Governors Association, told Democratic volunteers in Madison on Thursday that he thinks strong turnout could swing the election by as much as 5 points.

In the latest poll released this week Republican Gov. Scott Walker had a narrow 7-point lead over Democratic challenger Tom Barrett, just inside the margin of error.

O'Malley said given the fact that Walker has dramatically outspent Barrett in the campaign so far, it's a surprise the race is as close as it is. He said Wisconsin voters should take advantage of the chance to "make a midcourse correction."

O'Malley said the DGA has invested about $3.2 million so far in the race. He said that's more than the DGA invested in 2006 in former Wisconsin Gov. Jim Doyle's reelection and more than in 2010, when Barrett lost to Walker by about 125,000 votes.

Walker is campaigning with South Carolina Gov. Nikki Haley on Friday.

The recall election is set for June 5.