AVENTURA, Fla. — Freshly energized protesters are taking to the streets, members of Congress are being confronted in their districts by constituents angry over health care, and wealthy donors are turning fear into action.

Eight years after Republicans united after a stinging electoral defeat to oppose President Barack Obama, Democrats are channeling an even deeper anxiety over President Trump — and a far shallower defeat — into a newfound burst of organizing.

Party leaders, eyeing the huge protests last weekend and growing worries over the promised repeal of the Affordable Care Act, are hoping to recreate the mass movement that sprang up in 2009 and swept Republicans to power in the House and in governor’s races across the country — a Tea Party equivalent from the left.

And they are turning to the same playbook that guided their conservative counterparts in the aftermath of Mr. Obama’s election: creating or expanding a number of groups outside the formal architecture of the party, focusing on often-overlooked state legislative and redistricting campaigns, and bringing together frightened fund-raisers to underwrite it all.