"Nice to see you, nice to see you," McCain said to workers and passengers who greeted him on the 8 a.m. high-speed Acela Express train.
McCain, accompanied by a campaign aide, was left alone by the public as he sat in the first-class car for much of the 1 1/2 hour trip.
He drank coffee and read several newspapers - The Washington Post, The New York Times, Wall Street Journal and USA Today. And he talked on his cell phone with a campaign adviser for several minutes.
The night before, the Arizona senator had flown from Philadelphia to the nation's capital for votes on the federal budget.
As Republican presidential nominee-in-waiting, McCain had a campaign charter plane at his disposal.
But he took a commercial flight so that he could fly into Washington Reagan National Airport, nearer the Capitol, and he returned to Philadelphia by train.
In Washington, McCain tried but failed to attract support for a halt to pork-barrel spending, a moratorium on so-called "earmarks" sought by GOP conservatives to restore the party's credibility with voters.
His effort lost on a 71-29 vote, but McCain attracted support from the two Democratic presidential candidates,and .
McCain told reporters Friday morning the process was a "charade" that deserved more deliberation.
Later in Springfield, Penn., McCain told voters: "We were voting on major issues of profound consequences with no discussion, no debate and 10 minutes to vote.
"Anyone who had the misfortune of watching it will know how hard it is to do the Lord's work in the city of Satan," said McCain, who has served four-terms in the Senate.