In a sign that he will fight hard for votes among northern Democrats, former U.S. Sen. Mark Dayton picked Yvonne Prettner Solon as his gubernatorial running mate.

Dayton's choice of the three-term state Senator from Duluth puts his stake in the ground in the 8th District, a DFL-heavy stretch of voters who tend to come out in all elections.He is vying against DFL-endorsed Margaret Anderson Kelliher and Matt Entenza in an August DFL primary.

He will announce the pick in Duluth Monday morning and file for the office Monday afternoon in St. Paul.

The pick not only means that Dayton's ticket is complete in his run for statewide office but also sets off a scramble among Democrats in Duluth to fill the now-empty Senate seat. A Solon has been in the seat for more than three decades. Prettner Solon's late husband, Sen. Sam Solon, was first elected in 1972. Prettner Solon was elected after his 2001 death.

As of 8 am Monday, no one had yet filed for the Senate seat.

Candidates have until June 1 to file.

The pick means that all but Entenza and Independence Party's Tom Horner have announced their running mates out of the major candidates for governor.