Sen. John McCain derided Sen. Barack Obama's foreign policy experience yesterday while continuing to invoke his new best friend, Joe the Plumber, as an argument for the ills of the Democrat's tax policies.

Over the weekend, Sen. Joseph R. Biden Jr., the Democratic vice presidential nominee, predicted that his running mate would be tested by some international crisis in the early days of his administration. Seizing on the remarks, Mr. McCain declared, "We don't want a president who invites testing from the world at a time when our economy is in crisis and Americans are already fighting in two wars....

"We've seen the wrong response from him over and over during this campaign," Mr. McCain told a crowd of several thousand supporters at Robert Morris University. "He opposed the surge strategy that is bringing us victory in Iraq and will bring us victory in Afghanistan.

"He said he would sit down unconditionally with the world's worst dictators. When Russia committed aggression against Georgia, he said the invaded country should show restraint. He's been wrong on all of these."

In talking of his own foreign policy credentials, Mr. McCain pointed to his experience as a Navy pilot on the carrier USS Enterprise during the Cuban Missile Crisis in 1962.

"We had a target," he said. "I know how close we came to a nuclear war and I will not be a president who needs to be tested. I have been tested. Sen. Obama has not."

The Obama campaign dismissed the criticism, contending that Mr. Biden's observation was a statement of the obvious about any new administration.

In the latest of a cascade of Pennsylvania appearances by members of the Republican ticket, Mr. McCain also appeared to allude to recent statements from Rep. John Murtha, D-Johnstown, suggesting Western Pennsylvania was a racist area, and, after apologizing for that, noted that the region had a past marked by "redneck" traditions.

While he didn't mention Mr. Murtha by name, Mr. McCain seemed to have him in mind as he said disagreed with any criticisms of the region. "Western Pennsylvania is the most patriotic, most God-loving, most patriotic part of America," he said. "This is a great part of the country."

Returning to a theme that's filled his speeches since the final debate last week in New York, Mr. McCain said that the experience of "Joe the Plumber" showed the dangers of Democratic tax policies.

Joe Wurzelbacher, an Ohio resident, had questioned Mr. Obama's tax policies in an encounter with the senator last week. Since then, Mr. McCain has adopted Mr. Wurzelbacher as a virtual running mate.

"As he told Joe, he wants to ... 'spread the wealth around.' He believes in redistributing wealth, not in policies that grow our economy and create jobs and opportunities for all Americans," Mr. McCain said. "Sen. Obama is more interested in controlling who gets your piece of the pie than he is in growing the pie."

During their third and final debate last week at Hofstra University, the two men bidding for the most powerful job in the world took turns vying for the allegiance of Mr. Wurzelbacher, several times addressing him directly into the camera.

Last night, without citing any specific instances, Mr. McCain said that his opponents had been attacking Mr. Wurzelbacher.

"What's that about?" he demanded.

The assertion, which Mr. McCain also made at an earlier Pennsylvania stop, sparked a long-range rebuttal from Mr. Obama, who was campaigning in Miami.

"It was really amazing," Mr. Obama said. "He's decided to make up this notion that I've been attacking Joe the Plumber. Even though just yesterday, Joe himself said that's not true. And even though he knows full well that my plan will cut taxes for working Joes and small businesspeople all across this country to help them pursue their dreams."

The Democrat's tax proposal would mean tax increases for families earning more than $250,000 annually, but Mr. Obama has pledged repeatedly that it would provide cuts for 95 percent of taxpayers.

Reacting to the Republican's portrait of his opponent as an enemy of small firms, Sen. Bob Casey, D-Pa., a close Obama ally, said it was the Democrat whose policies offered aid for small businesses, like the one Joe would like to own after the national media spotlight moves on.

Mr. McCain's appearance on the Robert Morris campus was his third Pennsylvania stop of the day and his fifth in the last week. Earlier in the day in Harrisburg, the Arizonan gave essentially the same speech to a crowd of about 2,000.

One of them was Mary Lou Lawyer, 81, of Highspire, who said, "He's a veteran and that is one of the most important things. I cannot imagine a better president because he has been through so much. He's just got to be our president."

Mr. McCain's running mate, Alaska Gov. Sarah Palin, will return to the region tomorrow for a rally in Beaver, her third recent appearance in the state. The extraordinary attention to Pennsylvania flies in the face of recent polling results finding consistent double-digit leads for Mr. Obama.

But given the Democrat's multiple threats to capture recently Republican states -- such as Florida, where Mr. Obama campaigned yesterday -- the GOP team is under pressure to pry at least one big state from the Democrats' 2004 column. And Pennsylvania is it.

Mr. McCain acknowledged the long odds against him yesterday, but shrugged off the polls and commentary.

"They forgot just one thing, they forgot to let you decide," he said. "My friends, we've got them just where we want them."

Mr. Casey seconded the thought that the race may not remain as comfortable for the Democrats as it now appears.

"You know as well as I do it will tighten up," he said yesterday. "Even Bill Clinton didn't get to 51 percent [in winning Pennsylvania.]"