As the presidential campaigns refocus on November, they're zeroing in on digital domains. In fact, the Obama campaign has spent six times as much money advertising online as it has on TV so far, though that's certain to change.
And Republicans are fighting back with a new Facebook app called the "Social Victory Center." (You have to be a Facebook user to access the site.)
China is clamping down on social media as it grapples with a crisis over the escape of a high-profile dissident, apparently to U.S. protection. The case presents new difficulties for a Chinese leadership already struggling to deal with the scandalous downfall of a powerful politician, and it complicates U.S. Secretary of State Hillary Clinton's visit to Beijing this week.
Yet China's use of social media in dealing with these two recent crises has been a study in contrasts.