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"Rand Paul is a friend of mine but he is such a negative force when it comes to fixing healthcare," Trump tweeted. "Graham-Cassidy Bill is GREAT! Ends Ocare!"
The Graham-Cassidy-Heller-Johnson (GCHJ) legislation would shift Medicaid funding to states in a block-grant system - a set amount based on the number of enrollees in certain healthcare programs.
The current system for federal funding allocates money based on a percentage of the actual money spent by states, aimed at avoiding undershooting the correct amount due to unexpected costs.
The GCHJ would also shift the formula by which states receive funds, meaning many states would lose billions over the next 10 years while others would gain. Overall, federal healthcare funding would decline by $80 billion, according to the left-leaning Center on Budget and Policy Priorities.
Trump, in a tweet, was enthusiastic about the prospects of the block grants.
"I hope Republican Senators will vote for Graham-Cassidy and fulfill their promise to Repeal & Replace ObamaCare," the president tweeted. "Money direct to States!"
Paul, on the other hand, has argued the new bill would preserve large parts of Obamacare and does not fulfill the GOP's promise to repeal the law. Incidentally, the bill would also slash funding to Kentucky, Paul's home state.