By Jonathan Weber
(Reuters) - Montana Senator Jon Tester appeared poised for victory over Republican Representative Denny Rehberg early Wednesday in what would be a major win for the national Democratic Party as it solidifies its majority in the U.S. Senate.
With more than three-quarters of the vote counted, Tester was leading by 49 percent to 44 percent.
A Tester win would end a ferocious battle in which an estimated $40 million was spent in a right-leaning state with fewer than 1 million people. The majority of those funds came from groups outside Montana.
Tester, a farmer and former state legislator, won the seat in a 3,000-vote upset in 2006. This year, he stressed his rural Montana roots and his independence from President Barack Obama, who lost the state by a wide margin. Tester touted his advocacy for veterans and women's health while attacking Rehberg as irresponsible and untrustworthy.
Rehberg, a veteran politician and real estate developer who has held the state's single House seat for a decade, aimed to paint Tester as a true-blue liberal supporter of the president who was out of touch with Montana issues. Rehberg stressed his budget-cutting acumen and aimed to ride Mitt Romney's coattails in a state with a strong fiscal conservative streak.
Dave Parker, a Montana State University political scientist, pointed to a big turnout in the college towns of Missoula and Bozeman and unexpectedly soft support for Rehberg among older, rural voters as key factors.
Dan Cox, a Libertarian candidate, may also have hurt the Republican, Parker said.
"The spoiler may have been Dan Cox," Parker said, noting that Cox was drawing about 6% of the vote and was especially strong in rural areas that are normally heavily Republican.
The contest between two well-known incumbents was a toss-up throughout, polls showed. Both parties, along with the anonymous independent groups that have flourished since the Supreme Court threw out limits on corporate campaign spending, had long anticipated a tight contest that could decide the balance of power in the Senate - and they spent accordingly.
(Reporting By Jonathan Weber; Editing by Ciro Scotti)