TV viewership for Mitt Romney's acceptance speech at the Republican National Convention was down sharply from Sen. John McCain's speech four years ago, Nielsen reports. That combined with other data may signal a shift from TV to social channels, as Twitter saw 5 million RNC-related tweets this year, compared with 365,000 tweets for both conventions in 2008. "You are no longer tethered to that screen in your living room. ... It's incredibly transforming and freeing," says Adam Sharp, Twitter's director of government and news.