WASHINGTON — Sens. Barack Obama and Hillary Rodham Clinton will campaign together next Friday, the first joint public event for the former rivals, as the senator from New York returns to the political scene after losing the race for the Democratic presidential nomination.

Clinton has shunned most public appearances since her departure from the race on June 7. She resurfaced Wednesday to attend funeral services for "Meet The Press" host Tim Russert, and is expected at two events with Obama late next week.

On Thursday, Clinton will introduce Obama to some of her top donors at the Mayflower Hotel in Washington, a bid to smooth relations between her supporters and the presumptive Democratic nominee. She is also scheduled to speak to the National Association of Latino Elected Officials earlier in the day.

An Obama spokesman said the campaign is not ready to announce details of Friday's joint appearance.

Speaking to reporters yesterday in Jacksonville, Fla., Obama defended his decision a day earlier to opt out of the federal financing system for the general election after earlier pledging to seek a deal with Sen. John McCain, R-Ariz., to use public as opposed to private money. McCain continued to bash Obama on the issue yesterday, accusing him of breaking his word and of compromising his claim to credentials as a reformer.

But the decision is almost certain to give Obama an enormous financial advantage in the final eight weeks of the race. While McCain will be restricted to spending the $84.1 million that public financing will provide, Obama is free to raise and spend as much as he can.

The Obama campaign reports that he has already attracted at least 1.5 million donors, and some political observers believe he could amass $300 million or more to spend on the general election.

The campaign announced last night that it raised $22 million in May, a relatively small sum compared to his previous totals — he raised $55 million in February — but still $1 million more than McCain's May total of $21 million, the best showing so far for the Republican. McCain finished May with just less than $32 million in the bank, compared with Obama's $43 million, although about $10 million of Obama's total can be spent only after the party's convention in August.

Clinton, who bowed out of the Democratic contest on June 7, reported a $22.5 million debt at the end of May, more than half of which came from personal loans to her presidential campaign. She lent her own campaign nearly $2.2 million during the month, bringing her total personal investment in the campaign to $12.175 million. Clinton had $3.4 million cash on hand left for primary spending. She also had more than $23 million for the general election, money her campaign cannot use to pay off her debts.

The Associated Press contributed to this report.