A victory next month in Montana, where blacks make up less than 1% of the population, could help Obama convince superdelegates that he can win over white, working-class voters who have been the mainstay of Clinton's support.
The last Democrat to win Montana was Bill Clinton in 1992. President Bush won Montana by 20 percentage points in 2004.
Dennis McDonald, chairman of the Montana Democratic Party, called the contest between Clinton and Obama "fluid" with both appealing to many new voters. "I don't see either candidate having a decisive advantage right now," said McDonald, who is neutral.
McDonald, a rancher, had planned to move his 500 head of Angus cattle to new pastureland on Monday, but rescheduled the job so he could meet with Obama, who made his second visit to the state.
"It's wonderful for Democrats in Montana to have all this attention," he said. "We're accustomed to being ignored."
Schouten reported from the Obama campaign. Contributing: The Associated Press.