WASHINGTON (Reuters) - Democrats Hillary Clinton and Barack Obama would be marginally more active in enforcing anti-monopoly laws while Republicans Mike Huckabee and John McCain were harder to predict, antitrust experts said.

Overall, none of the leading presidential candidates is considered an antitrust maverick although Democrats have had a reputation for being more aggressive than Republicans in challenging mergers.

This party difference may even be disappearing. “This is about incremental changes for the most part, not a revolution,” said Bert Foer, president of the American Antitrust Institute.

Of the leading presidential candidates, most is known about Hillary Clinton’s views on antitrust because of her work as a senator and her role in her husband’s presidency.

If she is elected, “there’ll be a return to the Clinton era of antitrust, which was actually more centrist,” said attorney Mike Keeley of Axinn, Veltrop and Harkrider LLP.

Clinton is also one of the few candidates who has directly weighed in on an antitrust issue. In October she co-sponsored a Senate bill to undo a Supreme Court decision that tossed out a 96-year-old law barring manufacturers from dictating minimum prices -- a practice that hurts discounters.

CLINTON, OBAMA SEEN SIMILAR

Ben Sharp of Perkins Coie said he expected a Clinton administration would have a competition policy that was “serious and vigorous with a new emphasis on antitrust.” Sharp’s firm is counsel to the Obama campaign but he is not involved in the campaign work.

For example, the current Justice Department will likely approve a joint venture by SABMiller and Molson Coors Brewing Co, the second- and third-largest U.S. beer makers, said Sharp. “I doubt very much that it would have got approval under the Clinton administration,” he said.

Clinton and Obama likely hold similar views on enforcing anti-monopoly statutes, opposing price-fixing and other competition issues, according to several lawyers.

Obama’s time teaching law at the University of Chicago, where pro-market emphasis is strong, would affect his antitrust views, Sharp said.

But Hamilton Loeb of Paul, Hastings LLP disagreed, saying Obama had studied law at Harvard Law School, where “the prevalent antitrust theory was more moderate.”

“I don’t think that people see a real difference between Obama and Clinton” in competition policy, added Loeb.

Of the Democrats, former Sen. John Edwards, who is struggling after defeats in Iowa and New Hampshire, was the “most likely to be aggressive on antitrust,” said Keeley. Edwards has campaigned on a populist, anti-corporate greed theme.

The administration of President George W. Bush has been perceived as more relaxed, approving, for example, the controversial 2006 merger of Whirlpool Corp and Maytag Corp, despite estimates they made about 70 percent of U.S. washers and dryers.

One of the big antitrust cases of the past 20 years arose out of the Clinton administration’s decision to join with a group of states in 1998 to accuse Microsoft Corp of abusing its dominant position in computer operating systems.

“And then when a new administration (Bush) came in, they not only settled the case but excluded the staff who had worked on it,” said Foer of the American Antitrust Institute.

The Justice Department argues the remedy agreement was well-crafted and successful in addressing the court findings.

Loeb contends there has been considerable continuity over the past 20 years. Presidents George H. W. Bush, Bill Clinton and George W. Bush were all “pretty similar” in their enforcement policy, he said.

REPUBLICAN WILD CARD

Turning to the Republican race, former Arkansas Governor Huckabee, who won the Republican caucuses in Iowa and is one of the few non-lawyers in the race, is “the biggest wild card,” said Keeley. “There’s really no track record there.”

Sharp, of Perkins Coie, agreed. “He’s a relative unknown. I’d be reasonably surprised if he’d ever given it (antitrust) any thought,” he said.

McCain, who won the Republican primary in New Hampshire last week, talks tough on business issues but experts said he is more opposed to wrongdoing than to big business itself. “With McCain, his emphasis on attacking business appears to be based more on (concern about) fraud and waste,” said Keeley.

And Loeb, while calling McCain the hardest to predict, pointed to the senator’s role in getting Orson Swindle named to the Federal Trade Commission, the other U.S. entity that enforces competition law. Swindle, commissioner from 1997-2005, fought in Vietnam and was a prisoner of war -- like McCain.

“He turned out to be a moderate, ‘facts and circumstances’ kind of guy,” said Loeb.