TV viewership for last week's Republican National Convention dropped sharply from 2008.

But the convention was a hit online and on social networks, the latest evidence of the political conversation's gradual migration from traditional media to the Web.

There are many reasons this year's conventions may be less compelling than in 2008. Four years ago was a historic election that saw Democrat Barack Obama become the first black presidential nominee and then-Alaska Gov. Sarah Palin emerge as Republican Party star.

Hurricane Isaac drew at least some attention away from the largely surprise-free GOP gathering in Tampa, Fla., last week.

Little news also is expected at this week's Democratic convention in Charlotte, N.C., where Obama will be nominated for a second term.