The messaging battle over a pending overhaul of the U.S. tax code has begun. And while Republicans say they feel confident they will overcome the opposition this time around, a lingering defeat on health care continues to concern proponents.

The administration and congressional GOP leaders last week unveiled a framework for the still unreleased tax legislation. It immediately set off a cascade of reaction — positive and negative — as Republicans labeled it a middle-class tax break and Democrats called it a giveaway for the rich.

It is round two of a clash over the major tenets of the GOP agenda.

As they tried to repeal and replace the 2010 health care law earlier this year, Republicans found it difficult to overcome opposition from Democrats and major health care stakeholders. Democrats framed nearly every proposal from the GOP as a blow to coverage for individuals with pre-existing conditions and a massive, if not fatal, funding cut to the Medicaid program.

Public opinion was further swayed by late-night talk show host Jimmy Kimmel, who spent significant airtime assailing legislation from Sen. Bill Cassidy of Louisiana. As a guest on Kimmel’s show in May, the Republican senator had promised to advance a bill that would pass the “Jimmy Kimmel test” — an informal measure of whether people with pre-existing conditions would be jeopardized.