The historically huge Democratic presidential field is on the brink of getting a whole lot smaller, Sen. Cory Booker said in Iowa Saturday.

“I don’t believe people should stay in this just to stay in it,” the New Jersey lawmaker told supporters, warning that he may be the next to drop out if he’s unable to meet his fundraising goals by the end of the month.

“You either have a trajectory to win or not,” Booker said during his appearance at the Polk County Steak Fry in Des Moines, a major Iowa Democratic event that drew 17 of the remaining candidates for the 2020 presidential nomination.

“Right now, if we don’t raise $1.7 million, we won’t be able to make the investments necessary,” Booker said. “If we don’t have a pathway to win, we should get out of this race.”

Booker echoed comments his campaign manager Addisu Demissie wrote in a memo to campaign staff that was posted to Medium Saturday.

Only four contenders have the “money necessary to build and sustain the national organization needed to win,” Demissie wrote. That means the Dems’ candidate field “is about to narrow dramatically.”

Mayor Bill de Blasio abandoned his White House bid Friday, winnowing the group to 19 — still an all-time high.

The rest of the field used marching bands, drum lines, hundreds of yard signs and at least one fire truck to make their pitches to the more than 12,000 Democrats who attended what organizers dubbed the “Caucus Coachella.”

Booker’s announcement came after California Sen. Kamala Harris announced she’d be going all-in on Iowa in hopes of finishing in the top three. Both have struggled in national and Iowa surveys, with Harris polling in the middle of the pack and Booker struggling to move beyond low single digits.

Former Texas Rep. Beto O’Rourke, also polling near the bottom of the pack, spent Friday night at the steak fry camping ground with supporters. They marched carrying huge blue letters that spelled, “Hell Yes,” a reference to O’Rourke’s promise to outlaw and confiscate assault-style firearms.

The Iowa GOP mocked the event with a pun-filled press release about how “there’s a lot at steak” and encouraging caucus-goers to “grill” the candidates.

“Whether it’s forcing Americans to eat less cheeseburgers or getting rid of farting cows, Democrats’ rare, half-cooked ideas are struggling to find support,” Republicans said. “Iowans will certainly take note of their ridiculous hypocrisy.”

With Post wires