Rep. Adam Schiff’s (D-CA) Senate campaign is vastly outspending his rivals as he tries to lock up a first-place finish in next month’s primary.

Schiff is spending heavily as he tries to hold on to his front-runner status in the final month before voters decide who will advance to the general election contest. The Burbank congressman has consistently led his four competitors since last year in both fundraising and polling, though the margins are close and the race is still fluid.