Of the seven main candidates running for president, only one wants to keep the Affordable Care Act in place: the Democratic kind-of-front-runner Hillary Clinton. Everyone else wants to get rid of it.
Most Republicans would replace it by returning health insurance regulation to the states, although they would also lock in much of the ACA's new spending. Self-proclaimed socialist Bernie Sanders would replace it with a single-payer system—Medicare for all. It's a terribly inefficient and costly idea, as many pundits have explained.