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WASHINGTON — There was no presidential campaign announcement, only the tease of one as Joe Biden spoke to a room full of enthusiastic supporters at a conference of International Association of Firefighters here on Tuesday morning.

But there was an endorsement of sorts as Biden took the stage and union members chanted “Run, Joe, Run.” The former vice president didn't give them a definitive answer, instead encouraging them to keep that energy in reserve.

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“Save it a little longer, I may need it in a few weeks,” he said, before joking, “Be careful what you wish for.”

Biden is closing in on a final decision this week as his team eyes a possible April launch date for a 2020 presidential run.

In his first political address since the midterms, Biden on Tuesday tested out the message that would be at the heart of his candidacy: a passionate call for restoring what he calls the middle-class bargain, and an appeal for moving beyond the current pettiness of our politics.

Noting the iconic image of firefighters raising a flag at ground zero after the 9/11 attacks, Biden said the country was so unified then, but now "we seem to be at each other's throat.”

“Extremism is on the rise in this country,” he said. “Mean pettiness has taken over. You notice I get criticized for saying anything nice about a Republican — folks, this isn’t who we are.”

Biden drew a sharp moral and economic contrast with President Donald Trump as he prepares to potentially face him. He attacked Trump for proposing a budget that would slash Medicare to pay for a tax cut for the rich, and accused him of stoking divisions.

"We’re not able to be defined by race, religion, pride — we’re defined by those enduring principles of the Constitution,” he said. "In America everyone needs to get a shot. That’s what the next president of the United States needs to understand and that’s what I think this president doesn’t understand at all."