We're entering what is likely to be the nation's first billion-dollar presidential contest. That became clear when Sen. Hillary Rodham Clinton let it be known that she will forgo public financing in her presidential campaign. "The system, unfortunately, is not working," the New York Democrat said last week. "It doesn't have the confidence of the taxpayers, who do not check the box to make the contribution on their tax returns. So I opted out."

In the past, some candidates rejected public financing for the primaries. George W. Bush did that in 2000 and 2004. So did John Kerry and Howard Dean in 2004. Clinton would be the first to reject public money for both the primaries and the general election, if she gets that far. Her Web site invites supporters to contribute as much as $4,600. The fine print says, "You agree that the first $2,300 of your contribution is designated for the primary, and any additional amount up to $2,300 is designated for the general election." With that, she becomes the first major-party candidate since 1972 to solicit private contributions for a presidential general election.

Why is she doing it? If Clinton accepted public money, she would have to abide by spending limits—about $50 million in the primaries and about $84 million in the general election. Increases in those limits have failed to keep pace with the cost of presidential campaigns. As a result, any candidate who accepts public funding—and spending limits—may not be able to wage a competitive campaign.

Clinton is also doing it because she can. A candidate who expects to be taken seriously must be able to raise $100 million by the end of 2007. It's sort of the entry fee. According to The New York Times, Federal Election Commission officials and advisers to several campaigns think that each of the major-party nominees will be able to raise $500 million for the 2008 race. For each nominee, that would amount to nearly $750,000 a day from the beginning of this year to November 4, 2008. It's twice as much as Bush and Kerry each raised in 2004. And it's far more than the approximately $109 million each 2008 nominee would get by accepting public financing ($25 million in matching funds for the primaries and a grant of $83.8 million for the general election).

In the view of former FEC General Counsel Larry Noble, now a private election-law lawyer, "If you sign up for the public system, you obviously don't have the ability to raise private funds. You don't have the support out there." He predicted, "There is no serious candidate who's going to want to stay in the [public financing] system."

Will voters resent candidates who opt out of public financing? Probably not. "When the first candidate, George Bush, forwent public funding and no one seemed to care, it really opened up the doors," Noble said. "I don't think we're going to see any public outcry about it."

Clinton was right about the decline in public support for the system. In 1980, 28 percent of taxpayers checked a box on their income-tax returns to earmark a small portion of their tax money (then $1) to finance presidential campaigns. Now fewer than 10 percent check the box (now $3). Apparently, taxpayers do not want to see their hard-earned tax money spent on campaign ads.

Sen. John McCain, R-Ariz., a champion of revamping campaign finance laws, was asked on Tuesday whether he will forgo public financing if he seeks the GOP presidential nomination. McCain replied that his campaign hasn't yet discussed it.

"I don't think his party will let him do it," Noble said. "Neither party is going to want to nominate someone who is going to limit themselves in terms of the amount of funds they can collect and spend."

Spurred by the Watergate scandal, the current presidential campaign finance system was first used in 1976.

Thirty-one years later, it seems about to collapse and die. Will a new public financing system eventually emerge to replace it? Only if there is another major campaign finance scandal.