Sen. Dianne Feinstein could face a stiff series of obstacles as she vies for re-election in California in 2018.

Six years after receiving the most popular votes in any senatorial election in U.S. history, the five-term Democrat has seen sliding favorability ratings as liberals in the Golden State hammer her for not being tough enough standing up to President Donald Trump.

Six months before the 2018 primary, just 41 percent of likely voters in California — a plurality — back the 84-year-old Feinstein, a new poll from the UC Berkeley Institute of Governmental Studies found.

Twenty-seven percent of those polled back Feinstein’s closest challenger so far, Los Angeles-based state senator Kevin de León. A considerable 32 percent said they were undecided, which some experts said could open the door to an insurgent campaign from a political outsider.

“She should be farther ahead,” David McCuan, a political science professor at Sonoma State University in California, told the San Jose Mercury News.