This raises an important question: What is the best way for a president to achieve this end consistent with the party platform and campaign goals (not to mention many public preferences)? There are a number of options. One is to work with Congress to push for amendments to the Affordable Care Act (ACA) in ways that reduce healthcare costs. The challenge here is that both chambers of Congress are controlled by the Republican Party. It is unlikely that the partisan control of the House of Representatives will change with the November elections. The Democrats have a chance at reclaiming the Senate, but it's a toss-up -- the Democrats may take the Senate, but it may only see a leftward lean in the Senate median with a de facto need for supermajoritarian support in order to pass legislation of any significance. And amendments to the Affordable Care Act would absolutely fit the bill. The result is that there will be a political environment not ripe for major policy change, with potentially only incremental progress to be expected given tendencies toward obstructionism. In fact, partisan voting extends even to non-political but also to procedural votes. In short, Congress isn't likely to move much unless the Democrats take the Senate, and even then there will be marked potential for opposition obstruction.
Another option is to work with states to incentivize improving upon the federal plan. For example, we find marked variation in air and water quality standards in the states, with California standards being particularly higher. We might envision states opting into add-on plans that cap out-of-pocket maximums and deductibles, two of the plan costs that constitute massive barriers to individuals being able to use the plans by which they nominally are covered.
Which then brings us to changing health policy by way of executive order, which are legally binding orders given by the President of the United States. The challenge is that the public's view of executive orders tend to low, as Reeves and Rogowski (2015) show. They find that support for the use of executive orders tracks the public's evaluation of the president and the their beliefs in the rule of law (e.g., ensuring civil rights, civil liberties, mechanisms of accountability, etc.).
So there is a real risk in pursuing policy through this means. When the president works with Congress to achieve progress toward healthcare progress, in the face of obstruction, it becomes relatively easy to point to Congress (in particular, congressional Republicans) as the culprit in precluding movement from the status quo. We are seeing this in the context of the current battle to fill the Supreme Court vacancy held by the late Justice Antonin Scalia. That said, it is easy also for Republicans to say, "You elected Clinton, and what has she accomplished? Vote for us in 2020 and we'll let you decide how you spend your money." But amid a polarized setting, pursuing policy change by way of executive order may be smart, but it would have to work given that there would, in that case, be only one person to blame, using a tool not revered by the American public on principal (a trend that is consistent over time, though with public support for unilateral action higher in those contexts in which Congress fails to act). How Clinton continues this discussion with respect to executive orders (in this context and others) will give us valuable information as to how we can expect her to work with Congress and to what extent she will work toward a stronger presidency, albeit toward responsiveness to public needs by way of unilateral action.