The Bipartisan Campaign Reform Act (BCRA), commonly known as the McCain-Feingold law after its Senatorial sponsors, John McCain (R-Ariz.) and Russell Feingold (D-Wis.), was signed into law by President Bush in early 2002 after years of debate.
Among its many provisions, the law sought to eliminate unregulated "soft money" contributions to the national Democratic and Republican campaign committees and candidates for federal office. It also limits the use of "electioneering communications," also called issue ads, which are commonly viewed as thinly disguised political attack ads run by independent groups in the weeks leading up to an election.
These two issues represent the core of the myriad challenges to the BCRA and have sparked a mountain of briefs and opinions offered for the court's consideration on the issue from a wide range of voices.
Soft money is loosely defined as unlimited donations to political parties from individuals, organizations or unions intended to fund purported party building activities or state elections. Such contributions were first allowed by the Federal Election Commission (FEC) in the late 1970s to fund "non-federal" party exercises and remained largely unmonitored until 1991 when the agency began to require full disclosure of the funds.
According to FEC records, soft money raised by the national political party committees grew consistently over the past decade, from $86 million in 1992 to some $495 million in 2000 -- making it a key fundraising venue and the source of a large part of political television advertising.
While BCRA banned soft money contributions, it doubled the amount of so-called "hard money" contributions individuals can make, raising the limit from $1,000 to $2,000 per person to any candidate and no more than $95,000 total to political parties or candidates in any one election cycle, among other regulations.
Other changes in the 2002 reform law included limiting contributions from minors and banning the solicitation of contributions while on or using federal property, including making telephone calls to donors.
Opponents of the law, including the leading appellant, Republican Sen. Mitch McConnell (Ky.), and a litany of advocacy groups, quickly filed suit to challenge the BCRA's constitutionality.
Most of the challenges rest on whether the law violates First Amendment rights of free political speech and association.
Lower courts consolidated 12 lawsuits brought by more than 80 plaintiffs challenging some 13 different provisions of the law into one overall case dubbed McConnell v. FEC. A three-judge panel in federal district court in Washington, D.C., heard the first appeal and produced a lengthy and fractured ruling that it subsequently suspended pending the Supreme Court's review.
The high court's special session, weeks ahead of the start of its regular term on Oct. 6, will include four hours of oral arguments instead of the standard one hour in a nod to the case's many stakeholders as the U.S. political system steams toward the 2004 presidential election.
"It's a major step forward for the court to decide to hear the case as early as it did," noted First Amendment attorney Floyd Abrams, who represents McConnell, told the Washington Post in June. "It's very important to know what the rules of the game are going to be."
Lawyers from selected organizations will be given the opportunity to address the court during oral arguments and include the Republican National Committee, the AFL-CIO and the American Center for Law and Justice.
Lawyers for the Department of Justice, including Solicitor General Theodore Olson, will be the main contingent defending the law. In all, eight lawyers will address the court instead of the usual two.
Other groups involved the BCRA's Supreme Court review represent a broad spectrum of interests including the National Rifle Association, American Civil Liberties Union (ACLU), National Right to Life Committee, U.S. Chamber of Commerce, the California Democratic Party and lawyers for McCain.
Like other advocacy groups, the ACLU, in its brief, rigorously defends its ability to sponsor television advertising on political issues -- something the BCRA seeks to limit.
"Under any conception of the First Amendment, the ability of organizations like the ACLU to engage in public debate on critical issues of the day through any medium the organization deems appropriate, including broadcast ads, lies at the very core of constitutionally protected speech," its brief says.
Like other high-profile cases, the amicus, or "friend of the court", briefs filed on different aspects of the BCRA debate have also carried considerable weight. The authors include state governments, noted business experts and former lawmakers such as Sen. Fred Thompson (R-Tenn.) who chaired a Senate investigation into campaign finance abuses during the 1996 presidential campaign.
"The soft money fundraising and spending in that  election rendered all but meaningless the source and contribution limits that Congress had established in the 1970s in FECA," Thompson's brief says.
"Once soft money was placed in party coffers, the parties then used it for purposes that exploited loopholes in how such funds could be spent."
Audio tapes of the Supreme Court oral argument sessions will be released Monday afternoon, marking only the third time in its history the court has moved to satisfy public interest by immediately releasing tapes of its proceedings.
The court also created a special page on its Web site to house the hundreds of pages of documentation related to the case.