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Kicking off a public relations campaign including a Twitter assault on Congress to build support for his plan to avert the looming " fiscal cliff," President Obama today said he is doing his part and urged Americans to pressure lawmakers to do theirs.

"Middle-class families, folks who are working hard to get into the middle class, they're watching what we do right now. If there's one thing that I've learned, when the American people speak loudly enough, lo and behold, Congress listens," the president told a crowd of middle-class Americans at the White House today.

With the clock ticking, the president called on lawmakers to act on areas where they do agree and to extend middle-class tax cuts. "I believe that both parties can agree on a framework that does that in the coming weeks. In fact, my hope is to get this done before Christmas," he said, flanked by Americans who wrote to the administration explaining how they would impacted if tax cuts are not extended.

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The president did not, however, mention his insistence on raising taxes on the top 2 percent as part of a broader deficit reduction deal, opting instead to focus solely on tax breaks for the middle class. The administration estimates the typical middle class family of four would see its taxes rise by $2,200 if Congress does not extend the current rate.

The president spelled out in simple terms what that tax increase would mean for most Americans if a deal is not reached. "It's $2,200 out of people's pockets. That means less money for buying groceries, less money for filling prescriptions, less money for buying diapers," he said. "It means a tougher choice between paying the rent and paying tuition. And middle-class families just can't afford that right now."

Unveiling a new initiative, the president urged the public to take to Twitter and use the hashtag "#My2K" to push lawmakers to act, part of his continuing "outside in" approach to change in Washington.

"Tell members of Congress what a $2,000 tax hike would mean to you. Call your members of Congress. Write them an email. Post it on their Facebook walls," he said. "Some of you may remember that a year ago, during our last big fight to protect middle-class families, tens of thousands of working Americans called and tweeted and emailed their representatives, asking them to do the right thing. And sure enough, it worked."

Borrowing from his recent campaign slogan, the president said it's important for Americans to "send a message that we need to keep moving forward."