WATCH: In Hearing, Sens. Graham And Cassidy Defend Their Namesake Bill To Repeal Obamacare

Sens. Lindsey Graham, R-S.C., and Bill Cassidy, R-La., are defending their namesake health care bill before the Senate Finance Committee on Monday afternoon, but resistance from a handful of GOP colleagues may sink this last-ditch effort to repeal and replace the Affordable Care Act.

The bill's authors have made changes to the legislation in hopes of winning over holdouts. But it appears they may still fall short of the 50 votes needed — along with the vice president as tie-breaker — to pass the bill. And Senate Republicans are facing a Saturday deadline to act on the legislation under special rules designed to foil a Democratic filibuster.

Sen. Rand Paul, R-Ky., confirmed Monday morning that despite the last-minute changes, he's still a "no" vote. Sen. John McCain, R-Ariz., is also on record in opposition, so Republicans can't afford to lose anyone else. Maine Sen. Susan Collins and Texas Sen. Ted Cruz have also expressed reservations. Sen. Lisa Murkowski of Alaska is undecided but voted against other repeal measures earlier this summer. Some of the last-minute changes to the bill include extra money for Alaska, Maine, Kentucky, Arizona and Texas.

Forecasters from the nonpartisan Congressional Budget Office are expected to release their analysis of the bill's budget impacts Monday afternoon. But the CBO did not have time to predict how the measure would affect the level of insurance coverage. CBO forecasts of a spike in the number of uninsured people was a factor in the defeat of earlier Obamacare repeal efforts. Researchers at the Brookings Institution predict the Graham-Cassidy bill would leave 32 million more Americans without health insurance by 2027.

The bill would eliminate federally financed subsidies for people buying insurance on the individual market as well as the Medicaid expansion. Some of that federal money would be repackaged as "block grants" for the states. The bill would also make major changes to traditional Medicaid, capping the federal government's contribution. Over time, federal expenditures on Medicaid could grow more slowly than health care costs, shifting responsibility for those bills to state governments or patients themselves.

The bill would eliminate the requirement that most Americans obtain health insurance or pay a penalty. It would also allow states to ease restrictions on the insurance market, which critics say would lead to higher prices for customers with pre-existing medical conditions.