A protester holds a sign at a campaign rally in Portland, Maine. (Joel Page/Reuters)

The super PAC that has been leading the charge against Donald Trump aims to keep up the pressure on the Republican presidential front-runner, hoping to prevent him from securing enough delegates needed for the nomination before this summer’s convention.

“You’re not the nominee until you get 1,237 delegates, and I don’t see how Trump gets there,” Katie Packer, the GOP strategist helping lead Our Principles PAC, said in an interview Tuesday night.

Packer said supporters of the group — which spent nearly $13 million on a barrage of hard-hitting ads attacking the billionaire real estate developer — plan to confer over the coming days on a strategy. Among the issues under discussion are whether the super PAC should continue to pursue a broad media strategy or focus more narrowly on communicating with delegates in the hopes of swaying their votes if there are multiple ballots at the convention in Cleveland.

“We are going to continue to push forward,” she said. “We have some time to regroup and figure things out.”

Out of the $35.5 million in anti-Trump ads run by Our Principles PAC and other independent groups, nearly $16 million was plowed into Florida, where the brash New York businessman trounced Sen. Marco Rubio in his home state. But anti-Trump advocates were heartened by the fact that Ohio Gov. John Kasich prevailed over Trump in his home state, where the groups spent $1.35 million.

“We didn’t strike a death blow by any means, but we certainly made the needle that he needs to thread to get to 1,237 pretty impossible,” Packer said.

“Our goal was always to deprive him of Ohio and Florida, and the fact that we got halfway, we consider a win for the American people and the Republican party and certainly us,” she added, noting that the group's latest ads that accused Trump of being a misogynist and promoting violence got a lot of media attention. “For the last 72 hours, between our big push on the violence at his rallies and his quotes about women, he was on his heels having to defend himself.”

Donald Trump had a good night on March 15, but polls show Republican party isn't entirely behind the GOP front-runner. (Peter Stevenson/The Washington Post)

Still, it remains to be seen how much more money the wealthy conservatives who have been backing the effort will want put into an ongoing campaign. Some of the biggest contributors to Our Principles PAC — such as hedge fund executive Paul Singer and Arizona-based donor Randy Kendrick — were staunch supporters of Rubio, who is no longer in the race.

Packer said that going into Tuesday, the super PAC’s supporters had hoped to prevent Trump from winning both Florida and Ohio, but had felt that his loss in one of those states would still be a win. “The folks that have invested in our effort are very committed to stopping Trump, and if they still see a path, they will support it,” she said.