With his announcement Monday that he's out to unseat Gov. Brian Schweitzer, state Sen. Roy Brown ended months of speculation about which Republican might take on the popular Democrat. It should be an interesting affair.

Brown, who will formally announce his candidacy on a swing through Montana's larger cities on Thursday, has been a GOP legislative leader, which especially in recent years has meant strongly conservative views. But he'll face in Schweitzer a moderate Democrat who can talk economic development and tax cuts with anybody. And in recent years, few governors have come to office directly from the Legislative branch.

There was Stan Stephens, a veteran state senator elected in 1988, but Tom Judge, Ted Schwinden and Judy Martz all stepped up from the lieutenant governorship, while Marc Racicot moved up from two terms as state attorney general. (Schweitzer more or less came out of left field, earning prominence with his energetic but unsuccessful challenge to U.S. Sen. Conrad Burns before running for governor against Bob Brown in 2004.)

Schweitzer has been blessed with a strong Montana economy, which developed right on the heels of the tight-money session of 2003, and Brown appears to be ready to take aim at the increased state spending that came along with the good times. "If there is a blip in the economy, the taxpayers-funded surpluses will not be there to fund the new spending," he told the Billings Gazette Monday, warning that such a downturn could force tax increases.

But on another level, the coming battle looks to be rather personal. Brown and other GOP leaders were harsh critics of Schweitzer during the 2005 session, and when Brown ran for a senate seat in 2006, Schweitzer was quick to travel to Billings to campaign for his Democratic opponent, Margie McDonald, who outspent Brown by better than 2 to 1.

That history, coupled with enough ideological differences to spice up the campaign for the party faithful on both sides, should make for a real test of just how red-colored Montana still is in 2008.