Speaking on Wall Street last night, Senator McCain of Arizona sounded more like an economic populist than a proponent of the kind of unbridled free-market capitalism promoted by many who work on the trading floors nearby.

At a town hall meeting in Federal Hall, the presumptive Republican nominee for president endorsed a federal probe into speculation in the oil markets, a phenomenon that some analysts contend accounts for about a third of the escalating cost of crude.

“I believe there needs to be a thorough and complete investigation of speculators to find out whether speculation has been going on and, if so, how much it has affected the price of a barrel of oil,” Mr. McCain said in response to an audience member’s complaint about investors driving up the price of fuel and other commodities. “There’s a lot of things out there that need a lot more transparency and, consequently, oversight.”

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Mr. McCain also lashed out at the oil industry, which is the target of intense hostility from Americans confronting higher gas prices.

“I am very angry, frankly, at the oil companies not only because of the obscene profits they’ve made but at their failure to invest in alternate energy to help us eliminate our dependence on foreign oil,” the senator said. “They’re making huge profits and that happens, but not to say, ‘We’re in this so we can over time eliminate America’s dependence on foreign oil,’ I think is an abrogation of their responsibilities as citizens.”

As he argued that the gas tax holiday he has proposed would give relief to truckers and lower-income Americans, Mr. McCain also took some shots at economists who have questioned whether such a plan would provide real relief at the pump.

“They’re the same ones, I guess, that didn’t tell us about the housing subprime lending crisis. They’re the ones that didn’t tell us about the dot-com meltdown. And they’re the ones that didn’t warn us about inflation that’s coming up,” Mr. McCain said. “I have to fall back on the old adage that if you take all the economists in the world and put them end to end, they still wouldn’t reach a conclusion. So, I trust the people, not the so-called economists.”

Mr. McCain said much of the impetus for higher commodities prices was coming from India and China, but he added, “Any profit or manipulation by speculators, no matter where they are in the world, it has to be addressed and addressed seriously.” He did not elaborate.

On the issue of trade, Mr. McCain hewed to a more traditional Republican message. “I want a hemispheric free trade agreement,” he said, arguing that lower trade barriers would reduce market volatility. He also wholeheartedly endorsed an expansion of nuclear power.

The question-and-answer session, which lasted about 45 minutes, was the first of 10 Mr. McCain’s campaign had hoped to stage as weekly joint appearances with the presumptive Democratic nominee, Senator Obama of Illinois. Mr. Obama’s campaign said it is open to some such events, but not 10. “This town hall meeting probably would have been a little more interesting tonight if Senator Obama had accepted,” Mr. McCain said. “I strongly urge him to do this.”

Last night’s audience of about 200 was invited by Mr. McCain’s campaign, Mayor Bloomberg’s office, and other organizations. Fox News, which had exclusive rights to carry the event live, described the questions as “very friendly,” and said there was confusion between the network and the campaign about whether a diverse group of voters had been invited. Mr. McCain’s team said it planned to hold an online, “virtual” town meeting tomorrow with independents and Democrats, including former supporters of Senator Clinton.

There had been reports that the McCain campaign would use an empty chair to highlight Mr. Obama’s absence, but there were no chairs onstage at all. “These town halls are really about raising the debate, so there’s no reason to taunt him,” an aide to Mr. McCain said.