In the final days of the dead-even Montana Senate race, Sen. Jon Tester (D) and Rep. Denny Rehberg (R) are storming the state in last-ditch efforts to gain an edge in a contest likely to finish as close as any in the country.

Stuck for much of the past 18 months within the margin of error, this Tossup race is perhaps tighter than it should be given that Republican presidential nominee Mitt Romney is expected to win the state by double-digits.

Republicans are looking to firmly attach Rehberg to the Romney ticket in hopes of gaining a seat the party needs for any chance at winning control of the Senate. As a part of that strategy, Romney has cut a television ad for Rehberg, only the second general election candidate he has done that for. Democrats are hoping that independent voters and a significant number of Republicans will be willing to back Tester in a race that is a choice between two candidates — not between the two national parties.

Democrats say their optimism is based on Tester’s likability and the superior campaign he’s waged against Rehberg, a fellow statewide elected official who has hardly gone a day without reminding voters how often Tester voted in support of President Barack Obama. That includes a pair of memorable TV ads featuring twins who say they’re as tough to tell apart as Tester and the president.

Undecided voters in Montana historically break late in the campaign, and they tend to vote Republican. So even if the Tester campaign thinks it’s up by a few points with just a few days to go, that  lead could easily disappear as the campaign comes to a close.

“It’s obviously close, but the problem for Sen. Tester inside the numbers is he has locked down all of the Democrats he’s going to get,” Rehberg campaign manager Erik Iverson said. “The undecided voters are overwhelmingly Republican, overwhelmingly Romney supporters, and we feel pretty good about the fact that they’re going to break our way. As close as this race is, I would much rather be in our position than in Sen. Tester’s position.”

Any little bit helps, so Democrats are hoping for a boost from a Montana court’s Wednesday release of the investigative report into the 2009 drunken boat crash that injured Rehberg and two of his staffers, who were all passengers.

Meanwhile, a Democratic-aligned political action committee in the state is running a television ad aimed at getting Republicans to vote for the Libertarian candidate instead of Rehberg.

The Tester campaign has branded the senator as a Montana farmer who is taking on a Washington politician — one of us versus one of them. Backed up all summer by a string of TV ads that often featured Tester working on his farm, the strategy has been effective and has helped keep the Democrat within striking distance.

“Montanans vote for people who put our state ahead of any political party,” Tester spokesman Aaron Murphy said. “We value leaders who make responsible decisions, hold themselves accountable and fight for our freedoms. In this race, that person is Jon Tester, and a lot of Montanans will be voting accordingly.”

The upside for Tester is that a potential 10-point Romney win in Montana would barely be half of either of the winning margins President George W. Bush enjoyed in the Treasure State in his two elections.

The campaign committees and outside groups have spent more than $20 million in independent expenditures on this race, and the ads have taken a turn in recent weeks. Republicans viewed the recent ad by Montana Hunters and Anglers, a group with ties to Tester and Sen. Max Baucus (D-Mont.), as an admission that Tester needs help. The anti-Rehberg ad, which was clearly aimed at Republicans, ended with the message: “Vote Cox,” referring to Libertarian candidate Dan Cox.

But Rehberg needs some help, too, as evidenced by the TV and radio ads launched last week by the National Republican Senatorial Committee. After constantly hammering home ties between Tester and Obama, these ads highlighted the connection between Rehberg and Romney.

Now the candidates are making their final personal pleas for votes. Republican Sens. John McCain (Ariz.) and John Barrasso (Wyo.) joined Rehberg this week on his “Liberate Main Street” bus tour.

Tester is finishing up a four-day, 1,700-mile trek before spending the weekend at get-out-the-vote rallies in the state’s largest cities.