Up and down the dais, lawmakers chimed in with stories of constituents who had received similar notices. Republicans offered examples of people being asked to pay more.
Democrats countered by citing constituents who had been able to find lower-cost coverage than they have now. Ranking Democrat Sander Levin of Michigan said one of his constituents has been paying $800 a month for a BlueCrossBlueShield plan and managed to find comparable coverage for $77, after tax credits that lower the premiums.
Still, Levin added, "this has become a matter of legitimate discussion."
It could take months to sort out the balance of individual winners and losers. There's not a central source of statistics on how many people have gotten cancellations. Even the number of people who buy insurance individually is disputed.
It isn't the administration's fault, said Tavenner. "In fact the issuer has decided to change the plan; (they) didn't have to."
Obama's promise dates back to June 2009, when Congress was starting to grapple with overhauling the health care system to cover uninsured Americans.
"If you like your health care plan, you'll be able to keep your health care plan, period," the president said in remarks to the American Medical Association. "No one will take it away, no matter what."
Some immediately saw the promise as too broad to deliver on, given that health plans are constantly being changed by the employers that sponsor them or by insurers directly.
Nonetheless, Democrats in Congress devised a complicated scheme called "grandfathering" to try to make good on Obama's pledge. It shields plans from the law's requirements, provided the plans themselves change very little. Insurers say it has proven impractical.
The White House weighed in Tuesday, with spokesman Jay Carney saying the changes are part of a transition to better coverage. "The good news," he said, "is that for every one of these individuals who might have a plan that is almost by definition providing less than minimal benefits ... you are now being offered a variety of options, including options by the very insurer that covers you already, for new coverage."