Columbus, Ohio (AP) -- A weeklong period in which Ohioans could register to vote and immediately cast a ballot has ended with turnout that didn't quite match expectations.

Early returns show about 3,000 voters in Ohio's four largest counties took advantage of the disputed policy, a surprisingly low turnout to some elections officials.

The window was expected to benefit Barack Obama, as his campaign and advocacy groups pushed democratic-leaning groups such as college students and low-income voters to the polls.

The Ohio GOP had sued in federal court to stop the voting window but was unsuccessful.

Republicans argued the window could lead to widespread voting fraud because officials wouldn't have an opportunity to verify registration information before ballots were cast.

Ohio, with 20 electoral votes, remains a toss-up state.

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