"I had a great time today with @realDonaldTrump and believe we are getting closer to an agreement on health care!" tweeted Paul after golfing with the president Sunday.

It is not only Paul's opposition to the American Health Care Act that made the outing notable. He and Trump have a long history of butting heads, going back to when they were both vying for the GOP nomination for president.

Trump once referred to Paul as a "tiny guy" and a "nasty guy," before disparaging the Kentucky senator's golf skills: "I could play him a thousand times and never lose to him."

Ever since the AHCA's failure, Trump has waffled on who deserves the blame. At first he blamed Democrats but later he set his sights on the conservative Republicans in the House Freedom Caucus (who are aligned with Paul), suggesting that he would support ousting them in primaries next year.

The problem for Trump is that it is not only the most conservative Republicans who were resistant to the AHCA. A number of moderate Republicans were opposed to rolling back the expansion of Medicaid.

Any attempts to make a health care bill more palatable to the Freedom Caucus will likely result in stiffer opposition from GOP moderates, including in the Senate, where the GOP can only afford to lose two votes, assuming Democrats are united in opposition.