For California Rep. Dana Rohrabacher, the 2018 election might be his toughest bid yet.

The longtime Republican congressman narrowly trailed Democratic challenger Harley Rouda in a Monmouth University poll of registered voters in California’s 48th District released Tuesday.

Rohrabacher was behind Rouda in all three of the poll’s likely voter models. In the full sample of potential voters — registered voters in the district who have cast ballots at least once since 2010 or are newly registered — Rouda led the incumbent 46 percent to 43 percent, though that was within the survey’s margin of error.

Rouda had a strong lead among independents, a critical swing constituency in a district with more registered Republicans, with 49 percent saying they favored the challenger and 31 percent favoring Rohrabacher.

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