ST. PAUL, Minn. — Sen. John McCain’s vice presidential running mate may be controversial, risky and untested on the national stage. But at the convention Wednesday night, Alaska Gov. Sarah Palin proved to be an instant jolt of energy for a political party that has been worried and demoralized for much of 2008.

From the moment she was introduced Friday, Palin has been on the receiving end of an almost unprecedented barrage of criticism. On Wednesday night, she took the opportunity to answer back, and she put her critics — Democrats, the media and the Washington political establishment — on notice that she is ready for a fight.

Palin knew her targets and went after them one by one. It was an us-versus-them attack, designed to attach Sen. Barack Obama and the Democrats to the cultural elite and to tie herself and McCain to the values of the hard-working, God-fearing, patriotic middle of America.

But while her speech seemed aimed at energizing the Republicans’ conservative base, Palin also sought to introduce herself as a fellow reformer with a maverick’s spirit to match the message McCain hopes to send from here tonight and through the rest of the general election campaign.

There is consternation even within some parts of the GOP that McCain has recklessly risked the party’s chances of holding the White House by making a visceral decision rather than a thoughtful one. Palin’s foreign policy credentials will be a source of ongoing questions.

And her rollout has been anything but smooth: Her announcement that her 17-year-old unwed daughter is pregnant caused a media frenzy, and her record as a reform-minded governor and mayor was challenged by evidence that she had actively sought earmarks in Washington.

But the more that has been thrown at Palin, the more the McCain team has seen opportunity to use her critics to turn her into a figure of sympathy. After several days on the defensive, they tried Wednesday to go on the offensive, with Palin’s address the culminating event of the day.

With her speech, Palin clearly passed her first test in the national limelight. But in some ways, it may have been one of the easiest she will face in the 60 days until Election Day. Will a woman who inspired the faithful in the Xcel Energy Center wear as well with millions of undecided voters while enduring the daily buffeting of a campaign that can cause even the most experienced to stumble?

One Democrat watching the speech predicted that even Wednesday’s performance may end up hurting her. He argued that the first impression she has made could be judged as too partisan, too harsh and too political.

But the reaction among Republicans after the speech was universally enthusiastic.

All day, as the delegates awaited her appearance, McCain’s advisers were using the criticism heaped on her as a weapon, accusing the news media and others of trying to destroy Palin’s candidacy before she was even formally nominated.

But it was left to Palin, who was known to few Americans outside her home state just a few days ago, to deliver the real message, and the three-minute ovation that greeted her demonstrated why she has been able to unite this convention behind the candidacy of a presidential nominee who has often been at odds with his own party.

Attacked as lacking the experience to serve as vice president, she ridiculed Democratic nominee Obama, a onetime community organizer in Chicago, as even less experienced.

“Before I became governor of the great state of Alaska, I was mayor of my home town,” she said. “And since our opponents in this presidential election seem to look down on that experience, let me explain to them what the job involves. I guess a small-town mayor is sort of like a ‘community organizer,’ except that you have actual responsibilities.”

Derided by her critics as someone who comes from a town of fewer than 10,000 people, she went after Obama for his famous “bitter” comment about small-town residents, made at a San Francisco fundraiser.

“In small towns, we don’t quite know what to make of a candidate who lavishes praise on working people when they are listening, and then talks about how bitterly they cling to their religion and guns when those people aren’t listening,” she said. “We tend to prefer candidates who don’t talk about us one way in Scranton and another way in San Francisco.”

Nor did she spare Obama’s wife, Michelle. Invoking those same small-town roots, she said of her friends and neighbors and all those like them around the country: “They love their country, in good times and bad, and they’re always proud of America.” That was a reference to Michelle Obama’s comment earlier this year that, “for the first time” in her adult life, she was proud of her country.

Palin was equally tough in responding to her critics in the media and the political establishment who have greeted her selection with everything from skepticism to scorn to derision.

“I’ve learned quickly, these past few days, that if you’re not a member in good standing of the Washington elite, then some in the media consider a candidate unqualified for that reason alone. But here’s a little news flash for all those reporters and commentators: I’m not going to Washington to seek their good opinion — I’m going to Washington to serve the people of this country.”

Palin had plenty of help Wednesday. Three of McCain’s rivals for the nomination — former Massachusetts governor Mitt Romney, former New York mayor Rudolph W. Giuliani and former Arkansas governor Mike Huckabee — as well as Hawaii Gov. Linda Lingle roused the convention audience with a series of attacks on Obama and his running mate, Sen. Joe Biden of Delaware.

“Zero! Zero! Zero!” the crowd chanted at any reference to what the speakers said was the Democratic ticket’s combined years of executive experience. “Sarah, Sarah,” they cheered when Palin’s name was mentioned.

And it was her night and her show. After the battering of the past few days, Palin and the Republicans reveled together in her arrival on the national stage. But tougher days lie ahead, and those tests will tell whether McCain was wise in his choice.

As one McCain loyalist put it shortly before Palin took the stage: “(He) had to reburnish the reform credentials, and she does it. Frankly, it’s all or nothing. She’ll either float the boat or sink it. It’s classic McCain.”