Running late, he jumped out and started on foot for a security checkpoint that shimmered in the heat a 15-minute hike away.

"It's blue-collar to walk in," Casey joked. He was right on message.

Casey, a first-term senator, is in high demand here as a surrogate for Sen. Barack Obama - booked for 10 back-to-back media interviews yesterday alone. He enjoyed his time in the spotlight, cracking jokes and schmoozing with anybody who wanted his time.

Tonight, he is scheduled to speak to the convention in a coveted prime-time spot to make the case against Republican Sen. John McCain on the economy.

From now until Nov. 4, Casey will make it his mission to try to persuade the white, working-class voters who flocked to Sen. Hillary Rodham Clinton during the Democratic primary season that Obama is just like them and will fight for their interests. In a tightening race with McCain, the Obama campaign has intensified its emphasis on economic issues in recent weeks, employing populist themes.

Tonight's speech also has special personal resonance for Casey, and possible symbolism for other Democrats who oppose abortion rights. At the 1992 convention, his father, the late Gov. Robert P. Casey, was barred from the roster of speakers - in part because he wanted to mention the issue and had refused to endorse then-nominee Bill Clinton.

"Obviously, I'm thinking about him a lot," Casey said of his father. "There was a real opportunity missed there to hear from somebody who really understood what it was like to fight for the powerless - that was his life. I want to speak to some of those same concerns he had."

He said his speech would be five to six minutes long, would deal with the economy, and would involve some "contrast" between Obama's economic plans and what he said was McCain's record of supporting the economic policies of President Bush.

"I don't want to tell you a lot more," Casey said, reflecting the Obama campaign's tight discipline about leaks. "You've got to be economical with your words, though, and the longer you're in the Senate, the more long-winded you get."

Earlier this year, Casey broke with leading Pennsylvania Democrats who were behind Clinton to endorse Obama, who lost the state's April primary by 9 percentage points. Advisers to Casey hope that in addition to boosting the party nominee, this week will raise Casey's national profile even as he touches base with Pennsylvanians at luncheons and receptions.

As Casey stood at a spot on the Pepsi Center floor marked with white tape for an interview with NBC's David Gregory, the cameraman remarked that he used to work in Pittsburgh for WPXI-TV and "filmed your dad a lot of times."

"Can we get you to move back to Pennsylvania?" Casey said, a line he used with several former state residents he encountered in Denver.

During the NBC interview, Casey brushed aside questions about poll results showing that some Clinton supporters were not yet sold on Obama. "People don't know his story. . . . We've got to show them his heart, his story of overcoming obstacles," Casey said. "I think because he's so eloquent and graceful, people don't know he had to struggle."

When Gregory asked about the 1992 snub, Casey said that his inclusion on this year's convention program - as well as language in the Democratic platform that urges a reduction in the number of abortions in the country - was a "testament" to Obama. "Senators from both parties will tell you that he's always been willing to listen to other points of view," Casey said.

And so it went, as Casey extolled Obama and party unity to the Italian network TG2, to Reuters Television, the Hearst-Argyle chain of stations, National Public Radio, and several reporters not on his schedule who just approached and asked.

Later, Casey spoke to a luncheon of the Faith and Politics Institute, arguing that Democrats needed to talk more about their religious faith, in particular how it inspired them to "service" to "the last, the least and the lost."

Then it was off to a reception held by AIPAC, the pro-Israel lobby, atop the Denver Athletic Club, where Casey made brief remarks and then mingled with the crowd, recognizing several Democrats from around the country whom he had met before or who had donated to his Senate campaign against incumbent Rick Santorum.

"Thanks for taking my calls when you knew I was calling to ask for money," Casey said, shaking hands with Michael Baurer of Chicago.

"You'll always be my hero because you were willing to take on Santorum," Baurer responded.