WASHINGTON -- Sen. John McCain (R-Ariz.) was supposed to do a conference call with reporters Wednesday hitting Newt Gingrich on behalf of Mitt Romney's presidential campaign.

Things didn't exactly go as planned.

McCain did talk about the announced topic, how the number of earmarks in Congress increased when Gingrich was House Speaker from 1994 to 1998. But his attacks on Gingrich (R-Ga.) were vague and listless.

"I can't remember any specifics," McCain said at one point.

But when a reporter asked McCain about the increasingly "negative tone" of the Republican primary, that got the "maverick" off in a direction he was interested in going: campaign finance.

"I dislike it, and the fact is that we all decry negative ads and negative tones but it does move voters and as long as it moves voters it's going to happen," McCain said.

"As you know, I think the outside super PACs and others is so disgraceful that I'm ashamed of the United States Supreme Court in their decision on United," McCain said, referring to the 2010 Citizens United decision that allowed corporations to spend unlimited amounts of money in political elections.

The decision by the nation's highest court gutted rules put in place by legislation sponsored by McCain and then-Sen. Russ Feingold (D-Wis.) in 2002.

McCain went further.

"I predict to you there will be a major scandal associated with the Supreme Court decision on Citizens versus United. There is too much money washing around," he said.

The problem, as a reporter on the call pointed out, is that McCain and Romney are at odds on the issue of campaign finance.

Romney has decried the role of super PACs, calling them a "disaster." But his issue is not with the unrestricted giving. He has said he remains in favor of placing no limits on campaign expenditures. The only change he has said he would make is to do away with super PACs and let donors give unlimited funds directly to candidates and campaigns.

"We already have unlimited contributions," Romney said last month in an interview with Real Clear Politics. "The question is: Is the campaign going to be responsible for them or is the campaign going to not have control of its own message?"

McCain shrugged off the disagreement, arguing that jobs, the economy and national security are the key issues that voters care about.

He tried to turn the campaign finance discussion in a direction that was aimed at Gingrich, going after Sheldon Adelson, a Las Vegas casino magnate who is the largest donor to a super PAC supporting Gingrich.

"I note with some interest that a casino owner has given $5 million and his wife has now given $5 million, so you have one family throwing in $10 million into a primary race. I don't think that's what our Founding Fathers had in mind," McCain said.

And with that, Romney communications director Gail Gitcho promptly ended the call.

"Senator McCain, thank you very much for taking the time today," she said. "I appreciate your comments and we'll talk to everybody tomorrow."