UNDATED (AP) -- One in five Wisconsinites who are old enough to vote could head to the polls today for the spring election.

The Government Accountability Board bases its prediction on the turnout from similar elections over the past decade.

Last year's Supreme Court contest between Justice Annette Ziegler and Linda Clifford drew 19 and a-half percent of the voting age population. The last contested Supreme Court race before that generated an identical percentage of voters.

This year's Supreme Court race between Justice Louis Butler and circuit Judge Mike Gableman has been marked by a barrage of negative TV ads, mostly by outside interest groups.

Heavy snow in northern Wisconsin could also impact voter turnout today. Twenty percent of Wisconsin's eligible voters would be about 875,000 residents.

(Copyright 2008 by The Associated Press. All Rights Reserved.)

Polls are open statewide from 7 a.m. to 8 p.m. Voters can register at the polls.