In a fiery speech to the Congressional Black Caucus, Obama warned that Republicans hoping to seize control of Congress want "to do what's right politically, instead of what's right - period."
"I need everybody here to go back to your neighborhoods, to go back to your workplaces, to go to the churches, and go to the barbershops and go to the beauty shops. And tell them we've got more work to do," Obama said to cheers from a black-tie audience at the Washington Convention Center. "Tell them we can't wait to organize. Tell them that the time for action is now."
His speech acknowledged what pollsters have been warning Democrats for months - that blacks are among the key Democratic groups who right now seem unlikely to turn out in large numbers in November.
"It's not surprising given the hardships that we're seeing across the land that a lot of people may not be feeling very energized, very engaged right now," Obama said. "A lot of folks may be feeling like politics is something that they get involved with every four years when there's a presidential election, but they don't see why they should bother the rest of the time."
But he said he's just begun rolling back a devastating recession that's come down "with a vengeance" on African-American neighborhoods that were already suffering.
"We have to finish the plan you elected me to put in place," Obama said.
Summoning the joy many blacks felt at the election of the first African-American president and recalling the words of the late actor and activist Ossie Davis, he declared, "It's not the man, it's the plan."
Obama was treated to several standing ovations in the darkened cavernous center. But the hall grew quiet as Obama warned, "Remember, the other side has a plan too. It's a plan to turn back the clock on every bit of progress we've made."
Obama never spoke the name of the Republican Party, but repeatedly invoked its policies - and did name its House leader, Rep. John Boehner of Ohio, a favorite Obama target in recent days.
Members of "the other side," Obama said, "want to take us backward. We want to move America forward."
With polls showing his party facing a wide "enthusiasm gap" with the GOP, Obama sought to rally an important constituency in his speech.
"What made the civil rights movement possible were foot soldiers like so many of you, sitting down at lunch counters and standing up for freedom. What made it possible for me to be here today are Americans throughout our history making our union more equal, making our union more just, making our union more perfect," Obama said. "That's what we need again."
The caucus is a group reeling from ethics charges against two leading members, Democratic Reps. Charles Rangel of New York and Maxine Waters of California. Republicans are preparing TV ads spotlighting the cases, even though House trials are now not expected until after the November election.
Obama mentioned neither case in his 27-minute speech.
For Obama, the caucus dinner at the Washington Convention Center capped a week of concerted outreach to minority supporters, a traditional wellspring of Democratic strength.