Former Republican presidential nominee Sen. John McCainJohn Sidney McCainDon’t disrespect McCain by torpedoing his clean National Defense Authorization Act Meghan McCain rips Trump's 'gross' line about her dad Trump's America fights back MORE (Ariz.) said Sunday he’s worried the negative tone in the GOP campaigns could help President Obama win a second term in the White House.

“I think there's reason to be concerned about it,” said McCain on ABC’s This Week.

"I've been in very tough campaigns. I don't think I've seen one that was as personal and as characterized by so many attacks as these are.”

McCain, who has backed former Massachusetts Gov. Mitt Romney’s bid for the nomination, went head-to-head against Obama in 2008 in the most expensive and drawn-out presidential campaign to date.

But election and campaign experts are predicting that the 2012 road to the White House will set new records across the board.

RELATED: Super-PAC craze sweeps the nation

The veteran Arizona lawmaker said one of the biggest reasons for the large number of negative advertising campaigns in the GOP primary is due to super-PACs, which can collect an unlimited amount of money, thanks to a recent Supreme Court decision.

“Frankly, one of the reasons is the super-PACs,” said McCain, a long-time advocate of campaign finance reform. “And why do we have the super-PACs? Because of the ignorance and naiveté of the United States Supreme Court in the Citizens United campaign.”

“I think it has to do with the unlimited money, and I do not believe I've ever seen campaigns characterized overwhelmingly by negative attacks,” he said, depicting Nevada casino tycoon Sheldon Adelson as one of the most egregious offenders. 

Adelson and his wife have donated $3 million to former House Speaker Newt Gingrich’s campaign since the start of the year.