Industrialist Jack Davis spent nearly $4 million of his own money trying to win a House seat in 2004 and 2006. He says he is ready to spend another $3 million if he runs again this year in upstate New York.

But this time, the wealthy Democrat has deployed a new campaign weapon: a lawsuit.

On April 22, his attorneys will try to persuade the Supreme Court to strike down a provision of the 2002 campaign law (PL 107-155) that Davis contends treats self-financed candidates unfairly.

“The playing field is uneven to begin with,” he said from suburban Buffalo, N.Y. “The incumbent has so many advantages they don’t need this other advantage.”

The so-called millionaires’ amendment lets opponents tap their donors for more funding when facing wealthy competitors who hit certain thresholds for putting their own money into a race.

Watchdog groups worry that if the high court tosses out that part of federal law, it could have an impact on at least three of 24 state-level public finance systems.

Davis lost both of his earlier bids to oust Republican Rep. Thomas M. Reynolds from New York’s 26th District. Reynolds announced March 20 that he will retire at the end of this term. Davis has not yet firmly committed to a third try for the seat, though he appears to be headed that way.

Davis contends that the millionaires’ amendment harms him because once he spends $350,000 of his own money, the law permits his opponents to raise three times as much as otherwise would be allowed from each contributor. He also complains that triggering the millionaires’ amendment forces him to file extra campaign expenditure reports — documents that divulge campaign strategy.

“Nobody thinks an incumbent and challenger are on an even playing field to begin with. He’s willing to take on that burden,” said Andrew Herman, a lawyer representing Davis. “But he doesn’t understand why he has to take on an added burden of giving his opponent added contributions.”

A three-judge panel of the U.S. District Court for the District of Columbia didn’t buy that argument.

In an Aug. 9, 2007, ruling, the judges concluded that Davis’ free speech rights had not been violated because the provision did not impede Davis’ ability “to spend unlimited amounts of his personal wealth” and did not reduce the amount of money Davis could raise from his own backers.

In its decision, the court noted that the millionaire provision in the 2002 campaign law “is similar to statutes that permit higher contribution limits for candidates who agree to public financing of their campaigns.”

That worries supporters of public-finance systems in place in different configurations in nearly half the states.

Generally, candidates seeking public financing for their election bids must raise significant amounts in small contributions to qualify for matching public funds. But some states, such as Connecticut, will match bigger contributions if the candidate is up against a wealthy self-funder.

“A bad opinion from this court could do considerable damage to public funding, even unintentionally,” said Laura MacCleery, a lawyer at the Brennan Center for Justice at New York University.

That worries supporters of public-finance systems in place for presidential campaigns and, in different configurations, in nearly half the states.

“A bad opinion from this court could do considerable damage to public funding, even unintentionally,” said Laura MacCleery, a lawyer at the Brennan Center for Justice at New York University.

Some watchdog groups fret that if Davis wins his case, government matching fund systems in Connecticut, Arizona and Maine could become vulnerable to challenge.

If the Supreme Court agrees with Davis that giving higher contribution limits to rivals of self-financed opponents chills the speech of wealthy candidates, that “may undercut the viability of providing incentives in the context of public financing as well,” said Tara Malloy, a lawyer at The Campaign Legal Center.

Connecticut gives statewide and legislative candidates who agree to spending limits extra funding when they face off against rich opponents.

For example, a state representative who raises $5,000 from individuals in $5 to $100 increments gets $25,000 in additional funding from the state. If a rich candidate spends more, the state will match that spending level.

“It’s a provision meant to ease people’s fears that if you participate in this program, you’re not hurting yourself,” said Andy Sauer, executive director of Common Cause of Connecticut.

The 2008 election year is the first for the state program — funded through seizure of unclaimed property such as dormant bank accounts and unclaimed life insurance — and 44 candidates have signed up.

“This is the first real test,” Sauer said.

Arizona has a similar system of funding candidates who demonstrate broad support with small donations. Legislative candidates facing privately financed opponents can collect as much as $84,900, depending on how much they raise.

That program is funded by voluntary tax-credit contributions, and a surcharge on civil and criminal fines.

Maine finances its program through a $3 check-off on the state tax form and fines for campaign-law violations.

It provides public financing to candidates who agree to severely limit private contributions.

Alison Smith, co-chairman of Maine Citizens for Clean Elections, acknowledged the measure of nervousness among advocates for public financing. But she said she expects the federal millionaires’ amendment and state programs to survive.

“I think the court will make preserving political speech the highest priority,” Smith said. “You can’t make a straight-faced argument that scaling back money in political campaigns enhances free speech.”

The 2002 federal law allows a congressional candidate whose opponent spends at least $350,000 of personal money to receive contributions in sums higher than otherwise allowed.

The maximum individual donation normally is $2,300, but that can be tripled for those facing a self-funder. Political party committees that normally are limited to $40,900 in a House race can spend an unlimited amount once a foe crosses the wealthy-rival threshold.

“This evens the playing field for candidates who are challenging millionaires or who are challenged by millionaires; the individual who can go to McDonald’s, have breakfast with himself, write himself a $3 million check and have the largest fund-raising breakfast in history,” Rep. Thomas M. Davis III of Virginia, former head of the National Republican Congressional Committee, said in legislative debate quoted in the government’s brief.

Solicitor General Paul D. Clement argued in his brief that the provision “represents a modest and constitutionally appropriate attempt to counteract the perception that a candidate who is wealthy enough can buy a seat in Congress.”

In 2006, Reynolds was able to outspend Jack Davis by $5 million to $2.4 million and win — without taking advantage of the elevated fund-raising caps.

But as a self-funder who triggered the law’s provisions, Davis had to comply with additional disclosure requirements in 2006, filing a report every time his campaign spent another $10,000. His failure to file the forms in 2004 yielded a $251,000 Federal Election Commission fine that is on hold while his court case is pending.

A least six congressional candidates in 2004, 25 candidates in 2006 and 15 candidates so far this cycle filed FEC reports under the millionaires’ amendment.

Davis isn’t the only Democrat eyeing the seat that Reynolds is now relinquishing. A number of candidates from both parties are expected to contest the open seat. And no matter how much money Davis or another Democrat might spend, it still could be a tough race, given the Republican tilt of the 26th District. President Bush won 55 percent of the vote there in 2004.