Democratic Rep. Brad Miller received the death threat in a phone call Monday, one of hundreds the congressman's office has fielded demanding town-hall meetings on the health care proposal, said his spokeswoman, LuAnn Canipe.
She said the callers were "trying to instigate town halls so they can show up and disrupt."
Democratic lawmakers expected protests and demonstrations as they headed back to their states and districts over the August recess to sell health care reform legislation.
Earlier this week, White House officials counseled Democratic senators on coping with disruptions at public events this summer.
In the week since the House began its break, several town-hall meetings have already been disrupted by noisy demonstrators (including this Tampa town hall which devolved into shoving matches and catcalls).
On Friday, former Alaska Gov. Sarah Palin chimed in, calling President Barack Obama's health plan "downright evil" in her first online comments since leaving office.
She said in a Facebook posting that he would create a "death panel" that would deny care to the neediest Americans.
"The America I know and love is not one in which my parents or my baby with Down Syndrome will have to stand in front of Obama's 'death panel' so his bureaucrats can decide, based on a subjective judgment of their 'level of productivity in society,' whether they are worthy of health care," the former Republican vice-presidential candidate wrote.
Obama, a Democrat, campaigned on a promise of offering affordable health care to all Americans, as the United States is the only developed nation that does not have a comprehensive national health care plan for all its citizens.
He has proposed a system that would include government and private insurers. Republicans say that private insurers would be unable to compete, leaving the country with only a government-run health program. They warn that could leave Americans with little control over their health care.
The protests have drawn widespread media attention, and Republicans have seized on them as well as polls showing a decline in support for Obama and his agenda as evidence that public support is lacking for his signature legislation.
Pushing back, Democrats have accused Republicans of sanctioning mob tactics, and Senate Majority Leader Harry Reid accused protesters earlier this week of trying to sabotage the democratic process.