GOP heads toward showdown on Obamacare

Senate Republicans on Sunday unveiled the latest version of an Obamacare overhaul bill as they face a five-day window for passage and dwindling support within their own party.

Three GOP senators came out against the former version of the bill, including Rand Paul of Kentucky, John McCain of Arizona and Ted Cruz of Texas. Sen. Susan Collins, R-Maine, has not explicitly said she would vote against the bill, instead conveying she is leaning against it and it would be difficult for her to envision a scenario in which it would earn her support.

The legislation, which has commonly come to be known as Graham-Cassidy, was authored by GOP Sens. Lindsey Graham of South Carolina, Bill Cassidy of Louisiana, Dean Heller of Nevada and Ron Johnson of Wisconsin. It would transfer Obamacare's revenue to states in the form of block grants and would repeal the individual and employer mandates.

Critics of the bill say it does not provide states with enough time or federal funding to craft their own healthcare plans, and have pointed out that though the bill calls for health insurance coverage to be "affordable," it does not specify what percentage of income that means. Critics also worry coverage will become prohibitively expensive for people with pre-existing illnesses like cancer or diabetes.

The latest version of the bill projects increased in federal funding to votes from swing states Arizona, Kentucky and Alaska, which would have seen reductions under the previous version. It also requires states to describe how they would address pre-existing illnesses.