Over the last few months, sites like YouTube, Netflix and Digg.com have tethered themselves to Facebook — letting people sign in to their sites using their Facebook username and password. The tool, called Facebook Connect, has helped to firmly root Facebook at the center of social activity and information sharing on the Web, despite a strong challenge from Twitter.

Now Connect is elevating Facebook’s status in the political realm. Friday, the mayoral campaign Web site of Mike Bloomberg has rolled out the feature. Supporters can join the mayor’s social network “Mike Bloomberg NYC Community” with their Facebook user name and password and choose to broadcast their activities there back to their friends on the social network.

Mr. Bloomberg, who is running for a third term as New York City mayor, is not the first politician to link his campaign site to Facebook. Last year, the Obama campaign added Facebook Connect to its social network, MyBarackObama.com, in the final weeks of the presidential campaign.

Facebook Connect could ultimately give political campaigns more viral exposure for their online efforts. Campaign supporters who join Mr. Bloomberg’s social network can easily invite their friends to join them in various online activities; if they sign up to attend a political event, that gets transferred back to Facebook too. Users are presented with options to withhold any and all of this information from Facebook if they wish.

For other campaigns — Mr. Bloomberg does not solicit donations from the public — Facebook Connect could also be a powerful tool to aid with grass-roots fund-raising. Every donor could have the option to ask their presumably like-minded Facebook friends to make a contribution as well.

One challenge: Facebook, wisely accommodating privacy concerns, shares only the user name and the user’s profile photo with the sites that include Facebook Connect. That limited information does not help the Bloomberg Campaign contact supporters with borough-specific appeals or invite them to political events held in their neighborhoods. So the campaign is also asking everyone who signs in to its site using Facebook Connect for their e-mail address and ZIP code as well — which unfortunately makes the process a little less seamless.

Via-Bits