As the clock ticked down to the historic healthcare vote on Sunday and congressional leaders scrambled to get holdout Democratic lawmakers on board, the White House was all-a-Twitter.

White House staff used the microblogging site to keep the momentum going, keeping track of which Democratic lawmakers had changed their minds and decided to vote in favor of the bill, finally giving the party a narrow majority to pass it.

Their short text messages, known as tweets, also gave the nearly 2 million registered followers of the White House's Twitter feed a blow-by-blow account of how President Barack Obama was spending his time as the vote neared.

Obama's White House is increasingly using Internet media like Twitter, YouTube and Facebook to talk directly to Americans and mobilize grassroots support for the president's ambitious legislative agenda.

Twitter's 140-character messages offer an immediacy that is attractive to a White House known for being tightly controlled and keen to get its message out in a rolling, 24-hour-a-day cable news network environment.

It is a logical extension of their campaign strategy where they used the Internet and viral videos to spread their messages as quickly and as thoroughly as possible, said Dan Amundson, research director at the Center for Media and Public Affairs at George Mason University in Washington.

SECRET SERVICE PROBES TWITTER THREAT

The traditional thing everybody in Washington tries to do is speak past the media ... to speak directly to the public.

White House spokesman Robert Gibbs, a recent Twitter convert, made news on March 12 when he used the service to announce that the president was delaying his trip to Indonesia and Australia so that he could focus on healthcare.

Quizzed at a news briefing about his use of Twitter for the announcement, Gibbs said: Twitter is a quick medium to get information out and we'll probably use it more often.

Gibbs, who has more than 42,000 followers on his Twitter account, tweeted after passage of the healthcare vote on Sunday: It's 1:05 AM and finally leaving the White House ... spent some time celebrating with a proud POTUS -- not abt him he told us, but for America.

The ease of communication offered by Twitter has a downside. It also makes it easy for disgruntled citizens to make threats against public figures, including the president.

The Secret Service confirmed on Monday it was investigating a conservative blogger who New York's Daily News said used his Twitter account on Sunday night to call for Obama's assassination.

We survived the assassinations of Lincoln and Kennedy. We'll surely get over a bullet 2 Barack Obama's head, the blogger wrote, according to the newspaper.

Secret Service spokesman Malcolm Wiley told Reuters the threat was being investigated but he declined to say whether the man had been questioned or faced arrest.

With the growth of social networking sites we have seen more threats that way, Wiley said. That is just a reflection of society.

(Editing by Bill Trott)

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