Republican presidential candidate Donald Trump addresses supporters at a rally Aug. 3 in Jacksonville, Fla. (Evan Vucci/AP)

A super PAC backing Donald Trump's presidential bid plans to roll out a new television spot hitting Hillary Clinton as donors continue to invest large sums in the group, its top strategist said Friday.

Rebuilding America Now, which has received the blessing of Trump's running mate and campaign chairman, collected $3 million in new contributions this week, strategist Ken McKay said in an interview. On Sunday, Florida Gov. Rick Scott, the super PAC's national chairman, is scheduled to debut the group's new ad during an appearance on NBC's "Meet the Press."

The commercial will have a decidedly different tone than the super PAC's last one, an optimistic pro-Trump ad called "America Soaring." Instead, the new spot — which will air in battleground states including Ohio, Pennsylvania and Florida — will go after the Democratic presidential nominee.

"It’s a spot about conflicts of interest and impropriety and self-enrichment," McKay said.

Rebuilding America Now has reported spending $6.3 million so far on ads, giving it one of the largest profiles of a growing collection of pro-Trump super PACs. Only one other group has spent more: Great America PAC, led by former Reagan campaign director Ed Rollins, which has shelled out $7.5 million.

The Trump groups are still far behind the pro-Clinton super PAC Priorities USA Action, which has already raised more than $100 million and spent nearly $40 million.

"We’ve got to get to even," said McKay, adding that Scott has been a "tireless" fundraiser for the group since he came aboard in late July. Despite Trump's recent stumbles, McKay said there is mounting donor interest in supporting the effort.

"People bring up their concerns, but it doesn’t stop the fact that they want an outsider," he said. "They don’t want a career politician. The message I get back from people is that he is not a career politician — he is learning all the time how to improve as a candidate. Meanwhile, [Clinton] can never unlie."

The Washington Post reported last month that Trump and Indiana Gov. Mike Pence were open to headlining fundraisers for the group, a reversal of Trump's previous stance on super PACs. Such appearances are permitted by the Federal Election Commission, as long as the candidates do not solicit more than $5,000.

McKay said such events now look "likely" to occur, saying there have already been scheduling discussions. Trump campaign officials did not immediately respond to a request for comment.

Anu Narayanswamy contributed to this report.