The Democratic National Committee filed suit Monday to force the Federal Election Commission to rule on the legality of John McCain's decision to reject public financing for the presidential primary campaign after initially considering taking the federal money.

Mired in conflict between Democrats and Republicans over a nominee to fill one of four empty commission seats, the six-member Federal Election Commission lacks a quorum.

So the suit filed in federal court in Washington seeks court approval for the DNC to pursue legal actions against McCain.

The Republican National Committee denounced the suit as "total nonsense."

If the Democrats prevail, McCain will be limited in the amount he can spend before the GOP's Sept. 1-4 convention.

Last July, at a time when his campaign was struggling, McCain indicated that he would take matching federal funds for his primary effort. Later, he kept his campaign afloat by taking out a bank loan that, according to Democrats, promised the matching funds as collateral.

Once he became the presumptive GOP nominee, McCain's fundraising increased enough that he did not need the federal money -- or the restrictions on spending he would face by taking it.

In a press release, DNC Executive Director Tom McMahon referred to McCain's history of pushing campaign finance restrictions, saying the senator has an "apparent belief that the reforms he championed apply to everyone but himself."

The suit comes as McCain contemplates taking a federal grant of $85 million for the general election, and as he swipes at Democratic presidential candidate Barack Obama, the front-runner in the money race, for declining to say whether he will take such money.

dan.morain@latimes.com