The great winnowing has begun.

Rick Santorum is ending his White House bid Wednesday, becoming the latest in a series of presidential hopefuls to quit the race after poor performances in Iowa. The former Pennsylvania senator joins Mike Huckabee, Rand Paul, and Democrat Martin O’Malley, all of whom have also dropped out in the past 48 hours.

Santorum, a culture warrior and Christian conservative who won the caucuses in 2012, failed to garner a single delegate Monday night in the Hawkeye State, where he placed a distant 11th with just 1 percent support. He is expected to make his exit official in an announcement Wednesday night, two sources told CNN, and will endorse another candidate.

Like Rand Paul, Santorum’s candidacy was torpedoed in part by the rise of Donald Trump, whose populist demagoguery overshadowed his own blue-collar pitch as a Republican who would revitalize American manufacturing. A series of increasingly shrill debate performances, confined as they were to the so-called “undercard” debates, never moved the needle. And his focus on the importance of two-parent families—a subtle shift away from the strident anti-gay message that partly defined his 2012 run—failed to connect with voters.

With just $42,919 cash on hand and nearly $170,000 in debt at the end of December, according to F.E.C. filings, Santorum’s campaign was already running on fumes heading in to Iowa. Hours after the caucuses ended, he told The Des Moines Register that he would spend “a couple of days just thinking and praying, and figure out what we are going to do.” Whether those quiet moments of reflection will lead him to throw his support behind Trump, whose bizarre anti-debate event he attended last week, will be revealed Wednesday night.

Update: 8:00 P.M.: Rick Santorum endorsed Marco Rubio for president Wednesday, calling him a “tremendously gifted young man” in an appearance on Fox News, according to Politico. “So thankful & grateful for your support. Just not our year,” Santorum added in a tweet. “So today please join me in supporting @marcorubio.”