WASHINGTON — Senate Minority Leader Tom Daschle, D-S.D., continued to fall further behind his Republican challenger after midnight, trailing by 6,500 votes with 87 percent of the ballots in South Dakota counted.

The Senate race was still too close to call as of 1 a.m. EST with 120 precincts yet to report results, though President Bush had already pulled away with South Dakota’s three electoral votes. With more than 302,000 ballots counted, Daschle steadily was losing ground as a virtual dead heat widened to 2 percent.

Daschle’s race against Republican challenger John Thune, a former member of the U.S. House, has been an all-out battle, with the two candidates spending more than $40 million in a seesaw of bitter political advertising that has dominated the local airwaves. Daschle’s apparent vulnerability has made South Dakota’s Senate race central to the fight for control of the Senate and has lured massive national efforts to keep him in his seat, and to push him out.