Republican strategist Johnny DeStefano had a discreet Zoom call with GOP megadonor Rex Sinquefield in May to talk over a plan that would shake up the Missouri Senate race. Theiragenda: sinking Republican hopeful Eric Greitens.

DeStefano had been working with Sinquefield’s top adviser, Mary Ellen Ponder, and the two presented Sinquefield with a blueprint to demolish Greitens’ standing in the polls. Sinquefield saw Greitens, who stepped down as governor in 2018 amid allegations of sexual assault and recently faced accusations of child abuse from his ex-wife, as unfit for office. And top Republicans believed he would be a mortal threat to the party’s prospects of holding what should be a safe seat.

This year, putting one seat at risk would mean endangering Republican hopes of capturing the Senate majority in the November midterms. Sinquefield, a 76-year-old index fund pioneer, quietly plotted with DeStefano to launch a super PAC that would barrage Greitens with slashing TV advertisements starting in late June, about a month before the Aug. 2 primary. He seeded the group with $1 million just before the super PAC began the ad campaign that helped lead to Greitens’ defeat on Tuesday, when he was running in third place as state Attorney General Eric Schmitt was declared the primary winner.

The ad offensive was the most public part of a year-long, behind the-scenes campaign to stop Greitens from winning the GOP nomination for retiring Sen. Roy Blunt’s (R-Mo.) seat, which was described to POLITICO by more than a dozen people involved in the race.

Party higher-ups from Republican National Committee Chairwoman Ronna McDaniel to National Republican Senatorial Committee Chairman Rick Scott to GOP megadonor Steve Wynn repeatedly pressed former President Donald Trump to not back Greitens. The lobbying effort would extend to the eve of the primary, when McDaniel advised Trump to resist giving a late, full-throated endorsement to the former governor, who had been aggressively courting him.

On Tuesday — weighed down by a multimillion-dollar TV ad campaign and lacking the Trump endorsement he so coveted — Greitens’ hopes for a political comeback were extinguished.