Multnomah County Chair Jeff Cogen announced this morning he will not run for mayor of Portland in 2012.

"After thinking about it, I've decided there's a lot still to do at Multnomah County," Cogen said. "It does not feel like the right time to walk away."

Cogen was seen as a strong potential challenger to incumbent Mayor Sam Adams, should Adams decide to seek re-election. Cogen had said he was considering a run. But the county charter would have required him to step down during his first term as county chair if he ran for another office.

Now Cogen's decision leaves an opening for another high-profile candidate to jump into the race. The only viable challengers who have stepped into the race so far are former City Commissioner Charlie Hales and New Seasons co-founder Eileen Brady.

Cogen's announcement will surely come as good news to them, and to Adams, who is expected to seek a second term.