A Democratic poll shows a tight contest in the crowded race for California’s 49th District, with Democrat Mike Levin narrowly ahead of Republican Diane Harkey .

The district is one of three in Southern California where Democrats are concerned about possibly being shut out of the general election. Under the state’s primary system, all candidates run on the same ballot with the top two vote-getters, regardless of party, advancing to November. With multiple hopefuls on both sides, the concern is a split in the Democratic vote could allow two Republicans to get through.

A survey conducted by Tulchin Research showed 17 percent of respondents in the San Diego-area district backed Levin, a lawyer, while Harkey was in second with 15 percent, according to a Democratic group interested in the race. Harkey is a member of the state Board of Equalization, an elected body that oversees tax administration. The Republican incumbent Darrell Issa is not seeking re-election.

Doug Applegate, the 2016 Democratic nominee who narrowly lost to Issa, took 12 percent in the survey. Democrat Sara Jacobs and GOP state Assemblyman Rocky Chavez were both at 11 percent.

Trailing in single digits were Democratic businessman Paul Kerr at 7 percent and two Republicans, San Diego County Supervisor Kristin Gaspar at 7 percent and San Juan Capistrano City Council Member Brian Maryott at 6 percent.