Clothes still fluttering from the whoosh of the jackrabbit start of the 2008 presidential campaign, political experts say there are two possible and compatible explanations:

• The Beast must be fed -- in this case, the ever-expanding platforms of cable television, YouTube, blogosphere, e-mail and whatever else suddenly turns a bystander into a player.

• That wasn't really a zero-to-60 start the world witnessed when mere hours after Sen. Barack Obama secured the Democratic nomination, Republican nominee-in-waiting Sen. John McCain let fly with the kind of head-on rhetoric that once had to wait until late summer. The velocity of the primary contests merely swept in the remaining candidates.

"I think the truth is we were never at zero -- it's just that the race was waiting for two candidates, and now that we have them, hold on to your hats," said Susan Estrich, who managed the presidential campaign of Democrat Michael Dukakis 20 years ago.

Time was when candidates secured their delegates, spent the summer quietly laying plans, attended the convention, served up a stemwinder, then launched. Campaigns kicked off in September, or August at the earliest.

"Now, there is no August," says Ms. Estrich, a professor of law and political science at the University of Southern California.

We lost August. In June.

It vanished the night of June 3 when Mr. Obama took the same stage at the St. Paul, Minn., arena where Mr. McCain will formally accept his party's nomination at the end of August. He had already said Mr. McCain would be a mere continuation of the now unpopular George W. Bush administration.

"The American people didn't get to know me yesterday, as they are just getting to know Sen. Obama," Mr. McCain declared at his own rally, the same night, in Kenner, La.

Sen. Hillary Rodham Clinton hadn't even conceded the race. That wouldn't come for a few more days.

Neither man took the occasion to retire to his respective corner. A day off from what Reagan White House Chief of Staff Ken Duberstein calls "the perpetual campaign" would not come easily.

"It was a big deal that Obama took last weekend off," Mr. Duberstein said last week. "It's a big deal when McCain spends a weekend at his ranch. What we've come to expect now is all politics all the time."

Mr. Duberstein and a Democratic counterpart, former New York Gov. Mario Cuomo, both see a combination of voter engagement and an all-swallowing media vacuum that both campaigns are compelled to fill lest their opponent do it for them.

"Cable, YouTube -- all of that is totally different," said Mr. Duberstein. "When I was in the White House, we looked at the 12 o'clock news, the 6 o'clock news, the 11 o'clock news and what were the headlines the next day," he said. "Now, it is instantaneous. Cable is dying for content."

Another aspect of the seamless campaign, he added, is "jockeying for early advantage and defining yourself before your opponent gets to do it."

The prime example was 2004 Democratic nominee John Kerry, who shrugged off a viral campaign to disparage his decorated Vietnam combat record and re-cast him as a phony war hero.

This time around, with Republicans and hangers-on questioning everything from Mr. Obama's religion to a scheduled press conference tomorrow at which a shadowy group will try to paint him as a homosexual drug-user, the candidates aren't sitting still.

Just as Mr. McCain pushed back hard at The New York Times over a March story that suggested an improper -- possibly romantic -- relationship with a lobbyist, the Obama campaign has already opened its own pushback shop. It has a Web site dedicated to debunking the kinds of smear rumors that traditionally have waited for the end stages of campaigns.

Mr. Cuomo is hoping that kind of obsession for content can be channeled into something useful.

"You should be engaging them on the issues," Mr. Cuomo said, in a general plea to the media. "I'm glad it's starting early. Getting started earlier lets us get to the issues earlier."

Mr. Cuomo likened the 2008 election to the one that put Ronald Reagan, Mr. Duberstein's old boss, in the White House.

That year, he noted, Americans had gone through several years of self-doubt, a limp economy, energy worries and a slide in world esteem.

Now, with 80 percent of voters polled suggesting the country is on the wrong track, neither man sees any chance the race will slow down or dull out.

"Everything is just hyperventilating," Mr. Duberstein said.

Charlie Black, a longtime Republican consultant playing a key role in the McCain campaign, figures the intensity could be a legacy of the opposition, where voters energized by the prospect of the first woman to head a major party ticket versus the first African-American to do the same, stretched the primary process so long it somehow transformed into the general.

"People were intrigued by the Obama-Clinton race," Mr. Black said. "Maybe we picked that up.