Republican presidential candidate Donald Trump announced Tuesday that his campaign will debut its first ads in key early states.
"We're going to start some ads over the next two days," Trump said in an interview on Fox News. "Certainly in Iowa we're going to start ads, and in New Hampshire and, I think, in South Carolina too. We're going to start advertising."
Thus far, Trump has not spent any money on advertising -- a fact that he has routinely boasted about on the campaign trail and on debate stages.
But now, the GOP contender says that "we're going to start spending a little bit of money over the next three or four weeks." Trump added that he had planned to "spend 25 million by this time" in the election cycle and that he felt "guilty" not doing so.
"I feel guilty because I've spent nothing because we haven't needed it," he said.
Trump also gave a warning for Republican rivals that have heavily criticized him, naming Floridians Jeb Bush and Marco Rubio specifically.
"Anyone who hits me, we're going to hit ten times harder," he told Fox News. "As an example: Bush, Rubio. We're going to dollar for dollar go after them. We have more money than anybody else by a factor of a thousand. We'll go after them the same way."
The ad buys come just as the GOP candidate's nearly four-month lead in national polls continues to slip. According to a Quinnipiac University poll released Wednesday, retired neurosurgeon Ben Carson is in a virtual tie with Trump, lagging just one point behind the billionaire businessman.
Among likely Iowa caucus-goers, a CBS News poll from last week shows Trump and Carson both with 27 percent of support. Trump still leads by double digits in South Carolina and New Hampshire, according to the CBS survey.
Trump's campaign did not immediately respond to a request for more information about the ad buys.