WASHINGTON — The Supreme Court’s conservative justices appeared divided today over a campaign-finance law allowing candidates to receive larger contributions when their wealthy opponents spend heavily from their personal fortunes.

The so-called “millionaire’s amendment” kicks in to help candidates stay financially competitive against wealthy opponents.

“There is no restriction whatsoever on the wealthy candidate. He can spend as much of his money as he wants,” Chief Justice John Roberts said at the outset of arguments pitting Jack Davis of New York against the Federal Election Commission.

But Justice Antonin Scalia said he is “deeply suspicious” of the provision. “Trust our incumbent senators and representatives to level the playing field for us,” Scalia said.

The measure is part of the 2002 Bipartisan Campaign Reform Act, which the Court upheld in large part in 2003 in McConnell v. FEC. Last year, however, the Court’s conservative majority struck down a provision limiting corporate- and union-financed television ads in a 5-4 decision (FEC v. Wisconsin Right to Life) that suggested the Court would be hostile to federal limitations on money in politics.

Davis, a Democrat, lost in 2004 and 2006 to Republican Rep. Tom Reynolds.

Davis spent $2.2 million of his own money in the 2006 loss, but was vastly outspent anyway by Reynolds, who did not receive increased contributions after Davis reported exceeding the threshold, $350,000 in House races.

Andrew Herman, Davis’ lawyer, told the Court today that the law, in effect, says “we’re going to make it easier for your opponent to beat you.” Davis claims the provision unfairly protects incumbents who can easily tap campaign contributors.

Davis has already said he will spend $3 million of his own money this year to try and win the retiring Reynolds’ seat.

The FEC has said that only six incumbents were eligible to receive larger contributions because of their opponents’ use of their own money in the first four years the measure was in effect. Another 104 candidates faced opponents who spent enough from their personal wealth to trigger the provision.

The law also allows a political party to spend unlimited amounts of money to help a candidate facing a wealthy opponent, while the party of the wealthy candidate must abide by limits. Justice Anthony Kennedy said he was troubled by this aspect of the law because it appears to prefer “one kind of speech over another, and we simply do not do that.”

Solicitor General Paul Clement, representing the FEC, said there may have been just one campaign in which a political party took advantage of the limits being removed.

A three-judge court in Washington upheld the provision, saying Davis failed to show that his speech had been constrained by the millionaire’s amendment. It “does not limit in any way the use of a candidate’s personal wealth in his run for office,” the court said.

The case is Davis v. FEC, 07-320.