Phyllis Schlafly waves her hat as she leads her group to the Republican Platform hearing in San Diego in 1996. (Denis Poroy/AP)

ST. LOUIS — Phyllis Schlafly, the 91-year-old icon of the conservative movement, endorsed Donald Trump at his Friday afternoon rally.

“I know who you came to see, so I’ll be quick,” she quipped, miles away from the headquarters of her Eagle Forum organization in Alton, Ill. “I think he has the courage and the energy -- you know you have to have energy for that job -- in order to bring some changes. To do what the grass roots want him to do because this is a grass-roots uprising. We’ve been following the losers for so long — now we’ve got a guy who’s going to lead us to victory.”

Schlafly is a native of St. Louis, and the family of her late husband, John Schlafly Jr., has longtime ties to the city.

It was the latest in a series of endorsements from conservative figures who, having narrowed down the Republican presidential choice to Trump or Sen. Ted Cruz (R-Tex.), plump for the mogul-candidate's populism over the Texan's fealty to the cause.

For more than 60 years, Schlafly — an attorney who raised children then rushed headlong into conservative politics — had been a trailblazing grass-roots organizer. In 1964, she published the short tract "A Choice, Not an Echo," arguing that the Republican Party had courted defeat by allowing moderate nominees to be chosen in "backrooms." At the time, the GOP had lost ground in a series of presidential and midterm races, and Schlafly's voice was one of the loudest in favor of Barry Goldwater's 1964 presidential campaign, which cemented conservative control of the party.

Cruz has lavishly praised Schlafly. At last year's Eagle Conference in St. Louis, he spoke and took questions for the better part of an hour, pausing sometimes to praise Schlafly's life and work.

"Washington is suffused with a spirit of fear and timidity," said Cruz, with Schlafly in the front row of the conference she had organized. "That is a spirit Phyllis Schlafly doesn't even begin to understand. When she says a choice, not an echo, she means exactly that: A real, meaningful, conservative choice! Phyllis, I have to tell you, you inspire me."

But in the last few months, it became clear that Cruz might lose Schlafly's support to a member of her hated "eastern elites." After the first primary debate, Schlafly credited Trump with steering the Republican Party's discussion of immigration away from amnesty and toward deportation. When Trump called for a temporary ban on Muslims entering the United States, Schlafly told readers of her syndicated column that his idea was constitutionally sound. In a December interview with WorldNetDaily, Schlafly wondered whether it was time for the grass roots to back Trump.

"He does look like he’s the last hope," Schlafly said. “We don’t hear anybody saying what he’s saying. In fact, most of the people who ought to be lining up with him are attacking him."

The next month, in an interview with Breitbart News, Schlafly said that Trump seemed to be best positioned to defeat the "kingmakers" of the Republican establishment, but that Cruz should be his first Supreme Court nominee.

"That’s the place I think Cruz should go,” Schlafly explained. “He’s eminently qualified for that. And that would be a perfect solution for him … his qualifications are enormous."

The news of Schlafly's endorsement, broken by the conservative St. Louis blogger Jim Hoft, inspired quick criticism from the more mainstream right.

No public poll of the March 15 Missouri GOP primary has been conducted since August 2015, and recent elections there offer few clues as to which candidate might have the advantage. In 2012, former senator Rick Santorum (Pa.) won Missouri in a landslide, with a catch — it was a "beauty contest" primary that awarded no delegates, and did not include every Republican candidate. Santorum's 139,272 votes would not even have won him third place in the 2008 primary, which occurred on a historically busy Super Tuesday, and saw Sen. John McCain (R-Ariz.) edge out former Arkansas governor Mike Huckabee — McCain taking vote-rich suburbs while Huckabee won most of the conservative corners of the state.

Cruz's campaign manager, Jeff Roe, is based in the suburbs of Kansas City and has won several tough Missouri primaries.