Montana Republican Rep. Denny Rehberg has a four-point lead over incumbent Sen. Jon Tester, the Democrat who has voted for liberal bills like Obamacare, in one of the most important and hotly-contested Senate races in the country.

A Mason-Dixon poll conducted for Lee Newspapers poll found Rehberg with 49% and Tester with 45%. Five percent were undecided and one percent said they were voting for Libertarian candidate Dan Cox. 

Rehberg has gained one point from Mason-Dixon's last poll, which Rehberg led by three points. 

Brad Coker, managing director for Mason-Dixon polling, said it would be harder for Tester to make up ground with undecided voters in the closing days. 

“Rehberg’s just kind of kept that little lead on Tester,” Coker said. The general rule is it’s harder for an incumbent to make up ground with undecided voters. Here, you have two incumbents.”

In the poll, Rehberg led among men by ten points, seven among independents and was tied with Tester among women voters. The race is expected to be close on election day like Tester's election in 2006, which he may have won in part through fraud. 

The poll interviewed 625 likely Montana voters last week, and the margin of error was +/- four percentage points. 

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