The Jeb Bush Right to Rise super PAC will spend upwards of $15 million on its first major TV advertising blitz since raising $100 million to support the former Florida governor’s bid for the GOP presidential nomination, Fox News has learned.

Previous reports had underestimated the amount the high-powered PAC, headed by Republican political strategist Mike Murphy, will invest in the large ad buy, according to a source familiar with the specifics of the media campaign.

The television ads will be broadcast to potential voters across the early voting states of New Hampshire, Iowa and South Carolina.

They will begin airing September 15 and will run through the end of the year in all three states, according to Paul Lindsay, a spokesman for the super PAC. A second wave of ads will begin in early 2016, he added.

"It is the first phase of our sustained and independent campaign to tell Jeb's story and get the message out about his conservative record of accomplishment in Florida," Lindsay told Fox News.

Bush has slid six points among Republican primary voters in the latest Fox News national poll released Sunday--the first time he has dropped to single digits since April. He is now in fourth place in the national poll.

Fox News' Serafin Gomez contributed to this report