As Donald Trump savored his primary victories in Michigan and Mississippi Tuesday night, he also proclaimed himself a victim.

"I don't think I've ever had so many, many horrible things said about me in one week," the real estate tycoon said, referring the barrage of "horrible lies" filling the airwaves in primary states.

“That’s okay," he added. "It shows you how brilliant the public is because they knew they were lies, and it was just amazing to watch.”

He was correct on at least one point: we are now seeing the biggest engagement yet by anti-Trump groups in the 2016 race. Donors who last year assumed Trump's candidacy would eventually collapse are now pumping millions into groups running attacks ads against the Republican presidential front-runner.

To date, anti-Trump groups have reported spending $27.5 million hitting him on TV, online and in mailers — more than 10 percent of the $263 million that super PAC and other independent groups have poured into the White House race.

That's more than outside organizations have reported spending against all the other candidates combined, on both sides of the aisle. And it's a big uptick from just several weeks ago, when anti-Trump ads accounted for just 4 percent of super PAC spending.

Leading the charge has been Our Principles PAC, a super PAC backed by Marlene Ricketts, the matriarch of the family that owns the Chicago Cubs; billionaire hedge fund executive Paul Singer and conservative donor Randy Kendrick, among others. The group has reported spending $8.4 million through Tuesday night.

The lion's share of anti-Trump ads have rained down in the first eight days of March: $11.4 million in all. The question now is, is the campaign intensifying too late to prevent him from securing the GOP nomination?

One consolation for Trump opponents disheartened by his wins Tuesday: there was little effort mustered against him by independent groups in Michigan, where they spent just $42.86, or Mississippi, where they only put in $9,821.95.

The ultimate test of the #StopTrump effort will come Tuesday in Florida, which has seen nearly $12 million worth of attacks against the billionaire developer. But will it matter?

Weiyi Cai and John Muyskens contributed to this report.