David Langhorst is swapping a safe state Senate seat for a heated Ada County commissioner's race.

And that sets up one fascinating race this fall.

Langhorst, a Boise Democrat, is leaving the Legislature after three terms and says he will run for the commissioner's job held by Republican Rick Yzaguirre.

I can understand Langhorst's reasoning. Langhorst is a level-headed lawmaker who has tried diligently to cross partisan lines on transportation and air quality issues. He is also one of only seven Democrats in a 35-member Senate, and is probably tired of fighting those numbers.

However, the odds don't favor a Democrat winning a countywide election. Paul Woods won a commissioner's race in 2006 -- but with 43 percent backing in a narrow three-way race. A decade earlier, Frank Walker squeaked out a victory over lightning-rod GOP incumbent Gary Glenn. More than 113,000 residents voted in the race; Walker prevailed by 77 votes.

While Yzaguirre is an incumbent, he has baggage. In 2003, the former retailer admitted that he fell behind in submitting sales tax and lottery collections to state agencies. He has only appeared on a ballot once since then, in 2004, earning re-election with a scant 51 percent of the vote.

Obviously, this race will center on the growth issues both officeholders have dealt with for years. It could boil down to how the candidates play with their respective power bases.

Yzaguirre, a former Eagle mayor, has fared well in the West Ada County precincts that favor Republicans. However, last year's Eagle city elections suggest voters may be dissatisfied with the way local incumbents have managed growth issues.

Langhorst now represents Northwest Boise's legislative district, and is running for countywide office for the first time. How would he fare in getting out the vote in other Boise neighborhoods that tend to vote Democrat?

Langhorst has pulled a surprise before. His 2002 House win over moderate Republican Hod Pomeroy was a breakthrough in a swing legislative district. Four years later, Langhorst ran unopposed. That's the political job security Langhorst is leaving behind.