It's hard to argue against the fact that, like it or not, Twitter is a worldwide phenomenon.

Since the microblogging Web site launched in 2006, tens of millions of people have logged on and churned out billions of 140-character messages called "tweets."

Accounts of Iran's ongoing political tumult play out like breaking news on the site. So do life's trivialities — say, a humorous exchange with a dry cleaner.

And so does the U.S. government.

Congress has embraced the Twitter trend. Early last year, some 20 members were using the site, according to Tweet Congress, which monitors Members' Twitter use. The current count, the group says, is 162 (plus 16 committees and seven caucuses).

But any computer-savvy political junkie already knows that. Whether politicians are using Twitter to its full potential is another matter entirely.

"Twitter is wonderful and it allows you to blast information out very quickly," said Rep. John Culberson (R-Texas), one of the networking tool's early adopters. "Finally, America is achieving real-time democracy in a way that Mr. Jefferson would have loved."

At its best, Twitter is a transparent forum for unmediated exchange of ideas and ideals, and at its worst, a mouthpiece for narcissistic frivolities, say observers. It can be used for one-to-one, one-to-many, or many-to-one information sharing. And in Congress, tweets run the gamut.

Political birdwatchers can on any given day witness Members fielding constituents' questions or simply blasting one-way public relations hits.

"Media in general can be used for engagement or to be boring," said Dan Gillmor, digital media professor at Arizona State University. "For some (Members), there's a general desire to connect with constituents and others with social conversational media. I'm sure that for some, it's a completely cynical marketing exercise."

Republican members outnumber Democrats two to one on Twitter, according to Tweet Congress. By last count, including committees and caucuses, 123 Republicans tweet compared with 61 Democrats and one Independent: Sen. Bernie Sanders (Vt.).

Those figures are broken down further in a new report called Twongress, released this month by blogger and public relations executive Mark Senak. Senak found that as of the beginning of January, only 132 members actively use their account: 89 Republicans and 43 Democrats.

In the Senate, that includes 14 Republicans and 11 Democrats. Sen. John McCain (R-Ariz.) is the most popular user in Congress with almost 1.6 million followers.

The next most-followed member is Sen. Claire McCaskill (D-Mo.) with about 35,000, then Sen. Jim DeMint (R-S.C.) with more than 28,000 followers.

McCain's numbers almost certainly have to do with his presidential run, Senak wrote. President Barack Obama, after all, has more than 3 million followers.

In the House, the numbers are more one-sided. Active Republican representatives outnumber Democrats 75 to 32. Minority Leader John Boehner (Ohio) leads the pack with almost 19,000 followers and Minority Whip Eric Cantor (Va.) trails him with about 17,000.

In fact, only one Democrat is in the top ten on the House list — Dennis Kucinich (Ohio). Just two are in the top 20.