“As noted, despite calls to repeal the ACA ‘on day one,’ the President Trump, even with the support of a Republican Congress, was not able to repeal the legislation – although the vote in the U.S. Senate was very close. (Whether the House of Representatives would have passed the Senate bill is conjectural.) Due to arcane rules in the U.S. Senate, repeal before the U.S. National 2018 congressional elections will be extremely difficult because it would require 60 votes out of 100 – and Democrats and Democrat-leaning independents hold 48 seats.
“The Republicans were able to make a major legislative dent, however, by repealing the individual mandate. This was accomplished by including this provision in a major overhaul of the federal income tax system that passed Congress and was signed into law just before the end of 2017. Because Senate rules allow budget-related legislation to pass with a majority vote, the Republicans were able to succeed. The main reason was to fulfill, at least in part the promise they made to voters to repeal the ACA, but another was more pragmatic. Repeal of the mandate will reduce the number of people purchasing coverage from the exchanges, which in turn will reduce federal outlays. This allowed the Republican party to increase the size of the tax cuts that were included in the legislation.”
Source: Thomas Rice, Lynn Y. Unruh, Ewout van Ginneken, Pauline Rosenau, Andrew J. Barnes, Universal coverage reforms in the USA: From Obamacare through Trump, Health Policy, Volume 122, Issue 7, 2018, Pages 698-702, ISSN 0168-8510, https://doi.org/10.1016/j.healthpol.2018.05.007. http://www.sciencedirect.com/science/article/pii/S0168851018301544