Sen. Dianne Feinstein, D-Calif., endorsed Redlands Mayor Pete Aguilar for the Golden State’s 31st District on Wednesday, becoming the most high-profile Democrat to endorse in the state’s most contested congressional primary this cycle.

Aguilar, a Democrat who has the support of the Democratic Congressional Campaign Committee, has received the endorsement of the majority of California’s Democratic congressional delegation in a four-way Democratic primary.

But he faces several Democratic opponents: former Rep. Joe Baca, attorney Eloise Gomez Reyes, who is poised to receive the support of EMILY’s List, and school board official Danny Tillman. The quartet of Democrats is looking to unseat Republican Rep. Gary G. Miller in one of their party’s most sought-after seats in 2014.

In 2012, the party failed to win the seat when four Democrats split the primary vote and paved the way for Miller and another Republican to head to the general election, thanks to the state’s new top-two primary system. The seat got away from Democrats as President Barack Obama carried the district with 57 percent.

This cycle, the Democratic candidates have been sparring over endorsements for the seat.

After Aguilar announced endorsements from 10 California Democrats in Congress, Baca released the endorsements of many of his former colleagues in Congress. However, several of Baca’s endorsements reversed course in the following days.

The 31st District race is rated Lean Democrat by Rothenberg Political Report/Roll Call.