WASHINGTON — Just about a year and a half ago, Senator McCain went to court to try to curtail the influence of a group to which A. Jerrold Perenchio gave $9 million, saying it was trying to “evade and violate” new campaign laws with voter ads ahead of the midterm elections.

As Mr. McCain launches his own presidential campaign, however, he is counting on Mr. Perenchio, who is the founder of the Univision Spanish-language broadcast empire, to raise millions of dollars as co-chairman of the Arizona Republican’s national finance committee.

In his early efforts to secure the support of the Republican establishment that he has frequently bucked, Mr. McCain has embraced some of the same political-money figures, forces, and tactics that he pilloried during a 15-year crusade to reduce the influence of big donors, fund-raisers, and lobbyists in elections. That includes enlisting the support of Washington lobbyists as well as key players in the fund-raising machine that helped President Bush defeat Mr. McCain in the 2000 Republican primaries.

After enduring his own brush with scandal in the early 1990s, when he and four Senate colleagues pressured regulators on behalf of Charles Keating, chairman of a failed savings and loan association, while collecting donations and favors from him, Mr. McCain became a leader in the effort to eliminate “soft money” in elections — large donations from corporations, labor unions, and wealthy individuals. In 2002, Mr. McCain joined forces with Senator Feingold, a Democrat of Wisconsin, to finally push through legislation ending soft money and placing strict limits on donations.

But now, the contrast between Mr. McCain the presidential candidate and Mr. McCain the reformer can be jarring. Mr. McCain’s campaign says he is still studying whether to forgo the public financing and spending limits that he has long supported but that he will not be handicapped by restrictions his competitors will not face in 2008.

Mr. McCain the reformer worked unsuccessfully through Congress and the courts to try to stop nonprofit political groups known as 527s from using unlimited donations to run political ads and fund other activities aimed at influencing voters in the run-up to elections. He reintroduced legislation last week to end 527 donations, but there appears to be little appetite in Congress to pass it.

Mr. McCain the candidate now expects Republicans to use the same big-money 527 groups in the 2008 elections to beat Democrats, if the groups remain legal. “The senator believes that both parties should be subjected to an even playing field. If Democratic organizations are allowed to take advantage of 527s, Republican organizations will, too,” said Mark Salter, a senior McCain adviser. The senator declined to be interviewed.

Mr. McCain the reformer relentlessly argued that six- and seven-figure “soft money” checks that corporations, wealthy individuals, and unions were giving to political parties to influence elections were corrupting American politics. “The voices of average Americans have been drowned out by the deafening racket of campaign cash,” he warned just a few years ago.

Mr. McCain the candidate has enlisted some of the same GOP fund-raising giants who created and flourished in the soft-money system, including Mr. Bush’s fundraising “Pioneers” and “Rangers,” who earned their designations by raising at least $100,000 or $200,000 for his campaigns.

At least six of Mr. McCain’s first eight national finance co-chairmen have given or raised large donations for political parties or 527 groups, campaign, and IRS records show. In all, the finance co-chairs have given at least $13.5 million in soft money and 527 donations since the 1998 election.