Barack Obama is abandoning public financing for his presidential campaign, reversing his earlier stance in bold certainty he can raise millions more on his own as the first major-party candidate to bypass a system that was hurried into place after the Watergate scandal.

The Democrat has shattered fundraising records during the primary season, and he promptly showed off his financial muscle Thursday with his first commercial of the general election campaign. The ad, a 60-second biographical spot, will begin airing Friday in 18 states, including historically Republican strongholds.

Though it opens him to charges of hypocrisy, Obama's fundraising decision was hardly a surprise, given his record in raising money from private sources. Some $85 million in public money is available to each major party nominee for the fall campaign if they agree to forgo other contributions.

Despite Obama's decision, Republican candidate John McCain said his campaign will take public financing and added that he wasn't worried about being outspent in the fall campaign. McCain has lagged far behind Obama in fundraising throughout the contest.

He said Obama was going back on a promise to the public. "I strongly feel that Senator Obama ought to review his commitment not to me, but to the American people, which he has gone back on," the Arizona senator said at a campaign appearance in St. Paul., Minn.

McCain, long a proponent of tougher campaign finance laws, had committed to taking the public funds if his Democratic opponent did, too. By keeping his promise, he also gets another issue to use against Obama.

Obama has proven himself to be a prodigious fundraiser who could easily raise more than the public fund supplies. And while he and his advisers know McCain and other Republicans will criticize his decision, they understand that issues of campaign finance do not rank high in most voters' minds.

Obama will draw attention to his finances again Friday, when his campaign files its May fundraising report with the Federal Election Commission.

Obama's decision represents a significant milestone in the financing of presidential campaigns. President Bush was the first candidate to reject public financing of primaries when he ran in 2000. But no candidate has ignored the general election funds since the law setting up the presidential finance system was approved in 1976.

"It's not an easy decision, and especially because I support a robust system of public financing of elections," Obama told supporters in a video message Thursday. "But the public financing of presidential elections as it exists today is broken, and we face opponents who've become masters at gaming this broken system."

McCain sharply rebuked the Illinois senator on Thursday.

"This election is about a lot of things. It's also about trust," McCain said. "It's about keeping your word."

Last year, Obama filled out a questionnaire where he vowed to "aggressively pursue an agreement with the Republican nominee to preserve a publicly financed general election." But since clinching the Democratic nomination earlier this month, Obama has not broached the subject with McCain. The only discussion occurred about two weeks ago between Obama's and McCain's lawyers,

Obama lawyer Robert Bauer said he discussed the public financing issue for 45 minutes on June 6 with McCain counsel Trevor Potter. In interviews and e-mails, both Bauer and Potter agree that Bauer raised concerns about McCain having a head start because he had secured the nomination in early March and Obama did not until June 3. Potter said he told Bauer that given Obama's fundraising "I was sure there would be no McCain advantage by the end of the summer."

That meeting, Potter said, "was not part of any negotiation" on public financing.

"There was no aggressive pursuit of negotiations with the McCain campaign, there was no pursuit, period, of negotiations with the McCain campaign," Potter added later in a conference call with reporters.

At a breakfast with reporters Thursday, Bauer said that after his meeting with Potter, "It became clear to me, and I reported to the campaign, that there really wasn't a basis for further discussion."

Several campaign finance watchdog groups voiced dismay at Obama's decision, with Democracy 21 President Fred Wertheimer noting that the conditions Obama had initially set for accepting public funds had been met.

Sen. Russ Feingold, a Wisconsin Democrat who has worked with McCain on campaign finance laws in the past, praised Obama for his support of current campaign finance legislation, but added: "This decision was a mistake."

Obama raked in more than $265 million as of the end of April. Of that, nearly $10 million was for the general election, reserved for spending after the party's national convention in August. McCain had raised nearly $115 million by the end of May, eligible for spending before the convention.

McCain filed his May fundraising report Thursday with the Federal Election Commission, showing he raised $21 million during the month and started June with $31.5 million cash on hand. McCain had announced those numbers earlier this month. He spent a total of $11.7 million in May.

On the other hand, Obama's clear financial advantage over McCain is offset in part by the resources of the Republican National Committee, which has far more money in the bank than the Democratic National Committee. Both national parties can spend money on behalf of the presidential candidates.

Obama said McCain and the Republican National Committee are fueled by contributions from Washington lobbyists and political action committees.

"And we've already seen that he's not going to stop the smears and attacks from his allies running so-called 527 groups, who will spend millions and millions of dollars in unlimited donations," Obama said.

Despite that claim, few Republican-leaning groups have weighed into the presidential contest so far. In fact, Obama allies such as MoveOn.org are the ones that have been spending money on advertising against McCain.

McCain and Obama both declined public financing in the primary contests, thus avoiding the spending limits that come with the money. McCain had initially applied for the money, however, and has been in a dispute with the Federal Election Commission over whether he needed its approval to decline the funds. The FEC insists that he does, but has not had a quorum to act because four of its six seats have been vacant pending Senate confirmation of presidential nominees. McCain lawyers have disputed the need for FEC approval.

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