Demographically, the state would seem to suit rival Hillary Rodham Clinton almost perfectly - overwhelmingly white and rural. But political observers and a statewide poll suggest Obama has the advantage here.
The Illinois senator has outperformed Clinton in Rocky Mountain states, winning contests in Colorado, Idaho, Utah and Wyoming. Clinton won Arizona and a cliffhanger in New Mexico.
Only 16 delegates are at stake in Montana's primary, but depending on several other factors - what the Democratic National Committee rules panel decides this weekend about seating Florida and Michigan delegations and Puerto Rico's primary Sunday - the state could put Obama over the top for the nomination. He was about 40 delegates shy of victory on Friday.
South Dakota holds its primary the same day, but Montana's polls close an hour later, giving the state bragging rights to the finale in an epic marathon that has stretched from Jan. 3 to June 3, pausing in every state and spanning the globe as Americans living in dozens of countries cast ballots.
Clinton hopes wins in Montana and South Dakota will help persuade some of the nearly 200 yet-to-be-claimed superdelegates - elected officials and party leaders awarded a vote at the Democratic National Convention by virtue of their positions - to side with her and carry her campaign to the convention in August.
Three of Montana's eight superdelegates have endorsed Obama, while the rest say the outcome of the primary will help shape their decision.
More than 90 percent of Montana's residents are white and less than 75 percent have completed at least four years of college. The largest minority, American Indians, comprise about 7 percent of the population. Those are similar to demographics Clinton owned in earlier primaries.
But voters here may not fit the mold of the rural, working-class voters that backed Clinton in Appalachian and Rust Belt states. A recent poll showed Obama with a 17-point lead in Montana, although 13 percent of likely Democratic voters were still undecided.
Obama hopes a Montana victory will convince doubters that he can sway rural, white voters and compete against Republican John McCain in the Mountain West, where guns and the economy are key. Some political strategists contend Democrats have an opportunity to move three Rocky Mountain states - Colorado, Montana and New Mexico - into their column in the general election.
"The West shows in great contrast that Obama does appeal to this demographic they claim we don't do well with," said Obama state director Gabe Cohen.
Clinton's campaign has again turned to small towns, a strategy that has worked well in other states. Former President Bill Clinton has made five trips across Montana, stopping in places such as Havre and Lewistown that have never experienced such attention from a high profile political figure.
"If you add all the undecideds to her column, then you've got something approximating a dead tie in Montana," said Kenneth Bickers, a University of Colorado political analyst who has been tracking the race. "And at this point, she can't just tie. She has to beat him."
Clinton supporters are quick to point out that she does much better in primaries than in caucuses. And Clinton could benefit from her appeal to more conservative voters, another demographic she has courted.
Montana has a high percentage of gun owners, although it's hard to say who that would help - or hurt.
Gun owners remember, generally with disdain, the gun control measures of the Clinton administration. But Obama has gun control baggage of his own, which resurfaced after he was heard saying rural voters in small Pennsylvania towns "cling to guns and religion." In recent weeks, he has been trying to convince Western voters that "sensible" gun control won't get in the way of their traditions.
Political scientist Craig Wilson of Montana State University-Billings said he thinks Obama's comments about rural voters could be damaging in Montana.
"Some of that took a little luster off that big charisma," Wilson said.
But Obama may benefit from an early start in the state: He was first to open local campaign offices and was alone running TV ads until Clinton recently launched her first spot in the state.
The primary is open to all voters, and the Democratic race is expected to attract crossover Republicans and independent voters.
"It will probably be the independents who decide which way it goes," Wilson said.