SAN DIEGO (KGTV) - The candidate endorsed by retiring 49th Congressional District Rep. Darrell Issa will more than likely advance to the November runoff, but who she will be facing is less clear, according to a new 10News/San Diego Union-Tribune scientific poll.

In the SurveyUSA-conducted poll, Republican candidate Diane Harkey leads the race for Issa’s highly-coveted congressional seat with less than a week before the June 5 primary election.

According to the poll, Harkey leads by 24 percent of the vote, followed by Democrats Sara Jacobs and Doug Applegate at 11 percent each. Democrat Mike Levin comes in with 10 percent of the vote, with Democrat Paul Kerr and Republican Rocky Chavez both at 8 percent.

Click here to view the complete poll

San Diego County Supervisor Kristin Gaspar only mustered 5 percent of the vote, the poll showed. Thirty-one percent of those surveyed remain undecided.

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Under state law, the top two finishers in the June 5 election -- regardless of party affiliation -- will face off in the Nov. 6 runoff.

In the primary election for U.S. House of Representatives from California's 49th Congressional District, how do you vote?

Which one of the following issues is most important in determining how you vote in this election?

Do you approve or disapprove of the job Donald Trump is doing as President?

Do you approve or disapprove of the job Darrell Issa is doing as U.S. Representative?

The 49th District covers parts of coastal North San Diego County and southern Orange County.

Democrats have been fiercely trying to turn it blue since Issa narrowly won in 2016.

SurveyUSA’s poll results came interviews with 612 registered voters from the 49th District that were likely to vote in the state’s primary election. The survey was conducted May 29-31, 2018.

Click here to view the complete poll