Rob Portman

COLUMBUS, Ohio (AP) — U.S. Senate candidate P.G. Sittenfeld has made official his run against former Gov. Ted Strickland in the 2016 Democratic primary.

The 31-year-old city councilman from Cincinnati has resisted steady pressure from the Democratic establishment to clear the way for Strickland to take on sitting Republican Rob Portman next year.

Strickland, who has not yet filed, is the Democrats' endorsed candidate. His favorability and name ID exceeded Portman's in some early polling and he's already been targeted in more than $2 million in outside advertising.