4 days until votes are counted in the top-two primary in California's 49th Congressional District, the first finisher looks certain to be Republican Diane Harkey, who today takes 24% of the vote, according to this latest SurveyUSA poll conducted exclusively for KGTV-TV and the San Diego Union Tribune. Compared to identical polling released by SurveyUSA 7 weeks ago, Harkey has tripled her support, from 8% then to 24% now. High-profile incumbent Republican Darrell Issa is retiring; his seat in the U.S. House of Representatives is open.

16 total candidates are in the race, and 3 Democrats are tightly clustered in double-digits, but well behind Harkey, who is endorsed by Issa: Doug Applegate and Sara Jacobs each take 11% of the vote today; Mike Levin is nominally just behind with 10%. Applegate, who was Issa's 2016 opponent, is down a nominal single point since the last poll; Levin, an environmental attorney, is up a nominal point; Jacobs, CEO of non-profit organization and a former employee of the US State Department, is up 4 points, from 7% in mid-April to 11% today. Applegate draws support from moderates; Jacobs and Levin from liberals. Among those who have already cast their ballots, Levin has a small edge over his Democratic rivals. Among those who voted for Applegate in 2016, 26% stay with Applegate in next week's primary; 20% switch to Jacobs; another 20% switch to Levin.

Rounding out the crowded field are Democrat Paul Kerr and former front-runner Republican Rocky Chavez, each with 8%, and close enough, with 13% of likely voters still undecided, to potentially surprise when votes are counted this Tuesday 06/05/18.

Filtering and context: Using voter-list sample from Aristotle, SurveyUSA interviewed 700 registered voters from CA-49 5/29/18 through 5/31/18. Of the 700 registered voters, SurveyUSA identified 612 who have already cast their ballot or who are certain to do so in the 06/05/18 Top-2 primary. This research was conducted 100% by telephone. Respondents reachable on a landline telephone (60% of likely voters) were interviewed on their landline phone in the recorded voice of a professional announcer. Respondents not reachable on a landline phone (40% of likely voters) were interviewed by live operators, who hand-dialed cell-phone numbers, secured the respondent's cooperation, qualified the respondent, interviewed the respondent and remained on the phone until the conclusion of the interview. Under the rules of California's Top-2 Primary system, the 11/06/18 runoff could be between 2 Democrats, 2 Republicans, or 1 member of each party.