ST. PAUL - Once upon a time, John McCain promised to be a different kind of politician and a different kind of Republican. He was about straight talk, reform and nonpartisanship, a resolute foe of the slashing politics of the slaughterhouse.

McCain tried to get voters to remember that man in his acceptance speech Thursday night, the one who "worked with members of both parties to fix the problems that need to be fixed." But that man has disappeared.

The stage in the middle of the cavernous Xcel Energy Center was rearranged so McCain could conjure the feel of the town hall meetings he loves as he laced into "partisan rancor" and "the Washington crowd." Yet a set change could not disguise the fact that this convention -- including the big speech Wednesday by his running mate, Sarah Palin -- dripped with divisive ridicule as speaker after speaker worked to aggravate the country's cultural schisms and replay worn-out harangues against weak liberals.

The Republican crowd here gleefully played into the worst stereotypes of their party as a privileged class resistant to change.

When Rudy Giuliani referred to Barack Obama's past as a "community organizer" Wednesday, the crowd broke into ugly, patronizing laughter. These, presumably, are people who never needed a neighborhood advocate. Imagine if Democrats ever reacted that way to someone who worked as an entrepreneur or a church leader. And it's unlikely that even a convention of the American Petroleum Institute would erupt into raucous chants of "drill, baby, drill!"

McCain could not change his party, so he changed himself. McCain has pandered to a Republican right wing he once disdained on issue after issue, from oil drilling to immigration to tax cuts for the wealthy.

Just as important, he decided that his last chance for the presidency rests on a systematic effort to make the old politics of demonization work one more time. If McCain's convention is a prelude to the fall campaign, he will leave behind a legacy of bitterness that will turn his promise of a new day into ashes.

His single most cynical act was choosing Palin as his running mate, "cynical" being the word used by former adviser and friend Mike Murphy, the Republican consultant caught by an open microphone.

McCain knows that the first requirement in a running mate is preparation to succeed to the presidency. The choices he preferred, by all accounts, included Joe Lieberman and Tom Ridge, both plausible presidents.

But when it became clear that their support for abortion rights rendered both men politically toxic, McCain veered toward the last-minute pick of Palin. McCain barely knew her, and his campaign misled reporters about the extent to which she had been vetted. It was a political choice: Palin, McCain hopes, will help him win over women and rally social conservatives.

Palin's address here got boffo reviews from many of the very "reporters and commentators" whose good opinion the Alaska governor dismissed, but her speech was as cynical as the decision to put her on the ticket.

She joined in the campaign's fake populism by deriding legitimate concerns about her record, her knowledge and her governing style as the carping of the "political establishment" and the "Washington elite." She ran as the tribune of "small-town" Americans by way of suggesting that worries about her readiness to be president amounted to an assault on all who hail from localities of modest size. She dared to compare herself to Harry Truman.

She then proceeded to distort Obama's views on taxes, mock his eloquence and accuse him of wanting "to reduce the strength of America in a dangerous world." And she demonstrated how little she respects constitutional rights with this chilling declaration: "Al-Qaeda terrorists still plot to inflict catastrophic harm on America; he's worried that someone won't read them their rights."

But these thoughts, of course, were not really Palin's. They were words prepared by the campaign of John McCain, the unifier turned divider.

One night later, the unifier tried to come back, promising to reach out "to any willing patriot," criticizing his own party, urging that we use "the best ideas from both sides" and pledging to "ask Democrats and independents to serve with me."

It will be a hard sell because McCain has capitulated to the very Washington he condemned Thursday night and is employing the very tactics that were used ruthlessly and unfairly against him when he first ran for president eight years ago.

Perhaps the new McCain will somehow claw his way to the White House. But it's the old McCain who deserved to be president. A single speech on a September night is not enough to resurrect the man who might once have brought the country together.

E.J. Dionne's column is distributed by the Washington Post Writers Group.