The group Save My Care is targeting ads in the states of four Republican senators who are opposed to the GOP healthcare bill, calling on them to not buckle.

The pro-Obamacare group has targeted Sens. Lisa Murkowski of Alaska, Dean Heller of Nevada, Shelley Moore Capito of West Virginia, and Susan Collins of Maine. All of the senators have said they are opposed to the Senate health bill in its current form.

"The ads demand the senators keep their promise and stand up to any backroom deals and offers made by [Senate Majority Leader Mitch] McConnell and Republican leadership as they try to pass their repeal," the group said.

The ads come at a critical juncture for the senate bill as senators return Monday from a week off. The Senate only has a few weeks to pass the healthcare bill before leaving for a month long August recess.

McConnell can only afford two GOP defections out of Republicans' 52-48 majority. Vice President Mike Pence can break any 50-50 tie.