WASHINGTON — Long gone are the passionate debates. Long gone is the suspense about who will emerge as the party's presidential nominee. Political conventions now are carefully scripted pep rallies aimed at a national TV audience.

Not since the 1970s, in fact, has the nation had a major-party national convention begin with the nominee in doubt. Americans already know how the story will end at this year's Republican and Democratic national gatherings. So have modern-day conventions become irrelevant?

Not completely.

For the parties, conventions are colossally significant events — opportunities to claim precious hours of free prime-time television and showcase their nominees to millions. They preview the fall campaigns that are commencing and give the parties a chance to promote unity and excitement.

"Conventions have become more of a launch pad for the presidential campaign," says Stephen Wayne, a presidential scholar at Georgetown University and author of the book "The Road to the White House." "They excite the people. They excite the party base."

For most Americans, maybe not.

Plenty of people aren't focused in the waning days of summer on politics, government and the direction of the country. "People tune in for the final speech," says Wayne.

And for many, that's about it.

Nielsen ratings show about 22 million people watched the first full-coverage nights of the 2008 Republican and Democratic conventions, which featured speeches by Democrat-turned-independent Sen. Joe Lieberman of Connecticut for the GOP and by Michelle Obama and ailing Sen. Ted Kennedy of Massachusetts for the Democrats. The Republicans' opening session in St. Paul, Minn., was scaled back sharply as attention and concern focused on Hurricane Gustav's threat to the New Orleans area.

On the final nights of the conventions, about 38 million people tuned in for the nomination acceptance speeches of Barack Obama and John McCain — slightly more than the 35 million viewers who watched as the Summer Olympic Games opened in Beijing a few weeks earlier.