A big issue, according to Jon Lerner, a top consultant for the Club, is that while most Republicans believed Trump had a ceiling in the primary, he also had a floor. “At the root of it, what went wrong is that Trump had a lot of support, and Trump’s support was very solid,” says Lerner, who also worked on the main super PAC supporting Marco Rubio. Lerner points to the period — in December, January, and February — when, he says, he was seeing numbers that showed that Trump had a group of solid supporters who “were not going to move off him, and so . . . at least in my view there was no real prospect of hitting Trump with negative ads and moving a lot of his voters away from him.”

“But there was, I think, real reason to be hopeful that when the field narrowed, those kinds of attacks against Trump would succeed in preventing other voters from joining with Trump,” Lerner says.

Of course, for those hopes to have been realized, anti-Trump groups would have needed to follow a coherent, unified plan of action that made sense and maximized every dollar spent. For instance, Our Principles PAC, American Future Fund, American Future Fund Action Fund, and Club for Growth all ran attacks on Trump in Florida, where he held a large lead in the polls. And many of those ads began running after early voting had already begun, meaning they didn’t reach some portion of the Republican electorate. Trump ended up winning the state easily, ending Rubio’s campaign in the process.

It wasn’t the only such setback. The non-Trump contenders were all damaged by spending onslaughts, even as their chief antagonist largely proved impervious to outside spending on negative ads. Attacks from the super PAC backing Rubio damaged Chris Christie’s chances in New Hampshire. Spending by Right to Rise, the Super PAC backing Jeb Bush, kept Rubio’s poll numbers low leading up to the Iowa caucuses. But Right to Rise was a cautionary tale of the limited impact of paid attacks this cycle — the group spent over $100 million to help Bush, who dropped out after the South Carolina primary, having never placed higher than fourth place. And the attacks that truly damaged Rubio’s campaign were not backed by Right to Rise’s millions, but rather leveled at him in person: Christie’s attack on him as a robot at the New Hampshire debate, and Trump’s unflattering “Little Marco” moniker.