Updated

The U.S. Senate race in South Dakota appears to be focusing on a remarkably small number of undecided voters.

Recent polls touted by the campaigns of Senate Minority Leader Tom Daschle (search) and his Republican challenger, former U.S. Rep. John Thune (search), have differed on which candidate is ahead. But all the polls indicate that only a small fraction of the likely voters have not yet made up their minds in the race.

For example, two polls publicized by the campaigns in late August reported that just 2 percent of the voters questioned were undecidears, the last 18 in the Senate. Thune was in the U.S. House for six years before losing the 2002 Senate race to Democratic Sen. Tim Johnson (search) by 524 votes.

"It's almost as though you've got two incumbents running against each other," Smith said. "People have made up their minds."

Campaign managers for the two candidates said even if only 2 percent tell pollsters they are undecided, at least 5 percent or so are only leaning toward one of the candidates. The campaigns also are going after those voters who are not strongly committed.

Thune's campaign manager, Dick Wadhams, said 4 percent to 5 percent of the voters will probably swing back and forth between Thune and Daschle in the last few weeks of the campaign.

"We felt from day one that this race was going to be very, very close, and nothing I've seen has changed my opinion on that," Wadhams said.

Thune's advertising campaign in the final weeks will try to attract the small number of undecided voters and shore up support among Thune's supporters, Wadhams said.

Daschle's campaign manager, Steve Hildebrand, said Daschle's ads also will try to reach the undecided voters and those who have only weak support for Thune.