By Sharon Bernstein

SACRAMENTO, Calif. (Reuters) - Political consultants are sometimes accused of hiding the naked truth about the candidates they represent or the campaigns they devise.

But California voting expert Paul Mitchell bared it all after Tuesday's primary election, running naked around the grounds of the state Capitol building in Sacramento after his prediction in a key race turned out to be wrong.

"When improbable things happen, some pay consequences," Mitchell posted on Twitter early on Wednesday morning. Along with the posting was a photo of the darkened Capitol, a map of a running route from the athletic tracking app Strava and the title, "Streaking."

Last year, Mitchell firmly dismissed predictions that two Democrats would be chosen in Tuesday's primary to vie for the state's open U.S. Senate seat in November.

He was so sure that would not happen - despite a change in the state's open primary law advancing the top two vote-getters to the general election regardless of party affiliation - that he vowed to run naked around the Capitol if two Democrats were chosen.

When it became clear on Tuesday night that state Attorney General Kamala Harris and U.S. Representative Loretta Sanchez, both Democrats, topped the polls and would advance to the general election, Mitchell knew what he had to do.

He parked his car in front of the Capitol building in downtown Sacramento in the darkest spot he could find, took off his clothes (including shoes) and ran, he said in a telephone interview on Wednesday.

"I couldn't put up with all the badgering I would get if I didn't do it," he said. "There's honor among politicos, I guess."

He managed to maintain his privacy to all but a couple of youths on skateboards.

"It really doesn't seem like it's very dark outside when you're streaking," Mitchell said.

(Reporting by Sharon Bernstein; Editing by Peter Cooney)