The national Republican Party sued the Federal Election Commission Thursday, seeking to overturn prohibitions on unregulated corporate and labor contributions and to make it easier to coordinate spending with federal candidates.

In two lawsuits, the Republican National Committee directly challenged post-Watergate restrictions on the ability of parties and candidates to work hand-in-hand on political campaigns and the law Congress passed in 2002 banning unlimited contributions know as "soft money."

Republican National Committee Chairman Robert M. "Mike" Duncan said in an interview that the suits were designed to "strengthen the Republican Party and bring a more level playing field to campaign finance."

At issue are two distinct laws — one passed in the aftermath of the Watergate abuses of the early 1970s and the other a six-year-old ban on soft money. Both laws have been upheld by the Supreme Court, but since then the court has a new Chief Justice in John G. Roberts and a new justice in Samuel Alito.

The lawsuits come after the defeat of Republican presidential candidate John McCain, a fierce opponent of soft money and one of the authors of the 2002 legislation that banned the parties from raising unlimited money from corporations, unions and wealthy individuals.

The RNC lawsuit said the total ban on soft money amounts to a violation of the First Amendment's guarantees of free speech and association.

Critics say the suit is merely an attempt by the RNC to test the law against a reconstituted Supreme Court.

"This effort to go to the Supreme Court appears to be based on the idea that we have different justices so the prior decisions should just be thrown out, and that is just dead wrong," said Fred Wertheimer, president of Democracy 21, a campaign money watchdog group.

The RNC wants to be able to raise unlimited contributions for "non-federal" activities — that is, for expenditures unrelated to presidential, U.S. Senate or House of Representative elections. The money, the complaint says, would be used to help elect Republicans to state offices, to finance congressional redistricting efforts by state Republican parties following the 2010 census, and to finance lobbying efforts on federal legislative issues.

The RNC's effort to permit fundraising for state parties and state candidates would reverse a key component of the 2002 law that McCain helped write with Democratic Sen. Russell Feingold of Wisconsin and House members Christopher Shays, R-Conn., and Martin Meehan, D-Mass.

Under that law, the national parties can only raise money under federal fundraising restrictions. The law banned the national parties from raising so-called soft-money — that is, unlimited amounts of money from corporations, unions or individuals. If the national parties can raise money for state parties or for state candidates, they would adjust that fundraising to state limits, some of which are far more lenient than federal law.