The longest-running press conference in the history of presidential politics was into its umpteenth hour this morning when an aide to Arizona Sen. John McCain wandered to the back of the bus to interrupt.

The bus had come to a stop outside a high school in Manchester, but the senator was in mid-sentence on yet another question tossed his way from the knot of reporters squeezed into the benches and seats of the nicely appointed bus.

"Senator," the aide said with a mixture of hesitancy and urgency. "We have an event."

There is no predicting what will happen in the back of the McCain bus -- other than the non-stop question-and-answer session that ranges from the serious to the ludicrous and back again. McCain plants himself amid an ever-changing cast of reporters, puts on a pair of sunglasses that make him look rakish or roguish or just plain strange, depending on your point of view, and lets the conversation start to roll.

This morning it began with some talk about the Republican presidential debates and the dynamic that has been developing, or not, among the candidates. One thing McCain disclosed is that after he and magazine publisher Steve Forbes shared the makeup room before the first forum a couple of weeks ago, the Forbes campaign requested that, for the second forum, their candidate have his makeup applied alone.

Then it was on to McCain and his relationship with Texas Gov. George W. Bush, the man he is running neck and neck here in the state with the first presidential primary. The two have gone out of their way this week to say nice things about one another, but in truth, McCain says the two have been together about 10 times over the years. He confesses: "I don't know George W. that well."

On the first day of McCain's tour, he traveled with three buses. Today he was down to just two. The main bus is called the "Straight Talk Express." The second, which contains the overflow from the press corps, has been dubbed "Spin Buggy" by communications director Dan Schnur.

The buses are downright plush, with a shower, a flush toilet, carpet, cabinets, electrical outlets, televisions, you name it. Every morning the McCain team stocks the buses with cartons -- that's right, paper cartons -- of coffee from Dunkin' Donuts, and boxes of donuts and other things doctors don't recommend.

McCain's first event this morning was a town meeting in the small town of Weare, N.H., where he appeared to make some converts to the cause. Then it was back on the bus for a quick call to his wife Cindy and a resumption of the rolling press conference.

Among the passengers on this leg was Brenda Elias, a former mayor of Franklin, N.H., who is leaning to McCain but wanted to quiz the candidate about his views on Lebanon and the Middle East.

When he was done disgorging his views of the region, the reporters turned to Elias. What did she think of Bush? She was asked.

"A dilettante rich kid," she replied, before adding "And I don't dislike him."

It was on this leg of the journey that the first crisis of the day arose. McCain agreed to do an interview with a Swiss radio reporter. The day before he had done one with a BBC reporter and recalled the plaque he had once received from the Beeb for being a good interviewee.

The Swiss reporter huddled next to the candidate, microphone in hand, and began with a series of seemingly simple questions, like how important was New Hampshire. Then he got to the last one. Taking a leaf from the book of Andy Hiller, the Boston television reporter who stumped Bush on world leaders a week ago, he offered up this question:

"Can you name the capital of Switzerland?"

"Zurich. Geneva." McCain was struggling. "Do you know the capital of Arizona?"

The reporter finished up and then let out the bad news. "The capital is Bern," he said.

"I've now revealed my ignorance," he said.

As the reporters headed off the bus to watch McCain take questions from high school students in Manchester, he broke the news to his staff in the front of the bus. "I screwed up," he confessed.

They decided it was good preparation. After filing his papers of candidacy here in Concord at noon today, McCain was scheduled for yet another television interview -- this time with Andy Hiller himself.