The former Utah Democrsatic Party boss, who has worked as the government-affairs director for Zions Bank since 2003, said she could not do both jobs.

"Life is a series of choices and you make what you think is the best choice," Holbrook said, denying that poll numbers were a factor in her decision. "This is a different way to serve."

Holbrook said she wrestled with the decision for "a while," but is excited about the appointment by Gov. Jon Huntsman Jr.

"Our population may be 5 million by midcentury," she said. " I am excited to serve for the next six years as a transportation commissioner to help address these crucial statewide issues."

Poll numbers and anemic fundraising painted a difficult picture for Holbrook's mayoral chances.

A new Dan Jones & Associates poll conducted for the Deseret Morning News and KSL-TV showed Holbrook with just 2 percent of the vote.

And Holbrook reported raising $18,470 in campaign money by the first filing deadline in February, significantly less than financial front-runners Keith Christensen, Dave Buhler and Jenny Wilson.

Holbrook, who has not endorsed another candidate, intends to return her remaining funds to her campaign contributors after paying her mayoral expenses.

Nine declared candidates, including five major contenders, are now running in the nonpartisan contest. The field will be cut to two in a primary election Sept. 11.

- Derek P. Jensen