Green Party presidential candidate Jill Stein answers questions during a news conference at the National Press Club in Washington on Aug. 23. (Win McNamee/Getty Images)

In 1996, every major candidate for president participated in the public matching funds program. A Watergate-era reform, funded by a $3 voluntary checkoff on individual tax returns, it allows candidates to tap into free money so long as they abide by a spending cap. The fund has been in use since 1976, and it is credited for giving a fighting chance to political underdogs like Democrat Jimmy Carter and Republican Ronald Reagan.

But in 1999, George W. Bush bailed on the matching funds program; in 2007, Barack Obama did the same. This year, the Green Party's Jill Stein is the only presidential candidate, on most ballots, who is benefiting from the matching funds. So far, the Federal Election Commission has approved $456,035 in matching funds for Stein’s campaign. She is eligible to continue to make monthly submissions for public money.

Asked by The Washington Post why the Greens were taking the money — and whether, given the party's low historical level of support, it was warranted — Stein suggested that the question be put to the American people.

"They're screaming for an alternative," she said. "We have one Demo-Republican corporate party right now. What we call for is not simply expanding the ceiling for public funds — we want publicly funded elections."

The idea behind public financing was to level the playing field in presidential politics by equalizing spending. The fund now has $314 million sitting in reserve, but most candidates no longer apply for public money because of the spending cap.

Since fleeing the system, both major parties have experienced an explosion of private funding. In 2000, George W. Bush raised $192,636,228, while Al Gore raised just $132,804,039. In 2008, Barack Obama built an even bigger advantage over John McCain, raising $744,985,625 to the Republican's $368,093,763.

Campaign finance reformers have long argued that the program is outdated and no longer effective, but they want to save it with a massive overhaul. Democrats led by Rep. David E. Price (D-N.C.) have proposed legislation to increase the federal match to $6 in public money for every $1 raised by the candidate. The current match is 1-to-1. Republican critics of the fund have argued that it should be eliminated and the money sitting in the fund redirected to worthwhile programs or to the public debt.

In the meantime, the absence of the major parties in the system have lent it the appearance of farce. Democratic primary contender Martin O’Malley also qualified for public money; so far, he has been approved for just over $1 million in payments from the U.S. Treasury. O’Malley dropped out of the race in February, after winning no delegates in the Iowa caucuses, but the FEC approved an $8,000 payment for his campaign in April.