Conservatives, moderates force delay of Senate health care vote until after July 4 recess.
Top aides to Charles Koch, the billionaire energy magnate, said the Senate bill does not go far enough to dismantle former President Barack Obama's signature healthcare law, also known as Obamacare.
President Donald Trump can only afford to lose two GOP votes.
Without public buy-in or bipartisan support, any measure Republicans pass is likely to be temporary.
The Republican senators working on the Obamacare repeal-and-replace bill have received hundreds of thousands in campaign contributions from the two big lobbies.
McConnell wants to force a health care vote by July 4 and may bring the bill to the floor regardless of whether he has the votes to pass it.
Unable to vote down the legislation against a Republican majority, the Democrats are resorting to slowing processes in protest.
The 13 senators are viewed as key players to the Senate's Obamacare repeal.
There are worries that Republicans are leaning more toward the middle, angering senators who prefer the House's more conservative version.
Mick Mulvaney accused the nonpartisan Congressional Budget Office of intentionally showing the Trump administration's health care bill in the worst light.
Waivers added to House Republicans' bill would once again make insurance unaffordable for many with pre-existing conditions, posing a political problem for the GOP.
The House bill faces rough sledding in the Senate and the prognosis for sensible reform is bleak.
Republican lawmakers say that their legislative agenda is paralyzed by recent scandals.
Representative Rod Blum didn't like a television reporter's questions. So he left the interview.
One senator thinks the health care fight could drag on for a long while.
America has the only healthcare system in the world designed to avoid sick people.
The former U.S. president said the sick and infirm need champions and praised the Democrats who first passed Obamacare.
"Women's health is a big part of this and women are a majority of the population, and their health interests deserve to be contemplated in any reform," Democratic Senator Dianne Feinstein of California said.