Santa Rosa City Councilwoman Erin Carlstrom confirmed Wednesday that she is dropping out of the race for state Senate.

Carlstrom said she ended her campaign because Sonoma County Supervisor Mike McGuire had entered the contest, raising concerns the pair would split the vote and give someone outside the county an opening.

"I got into the race because I wanted to make sure we had strong candidates from Sonoma County," she said.

Carlstrom's departure leaves an all-male field vying to replace Sen. Noreen Evans, who announced that she is not seeking re-election in 2014 in order to return to her private law practice.

In addition to McGuire, Chris Lehman, a 36-year-old Arcata resident, political consultant and fundraiser, and Eric Lucan, 32, who was elected to the Novato City Council in 2011, have entered the race.

Carlstrom said Wednesday that she has not decided whether to seek McGuire's supervisorial seat. Because the 30-year-old attorney lives in Santa Rosa's junior college neighborhood, she would have to move to the North County district in order to run.