The 2010 Affordable Care Act (ACA) just reached its second birthday, and this week, the Supreme Court will consider whether it will see its third. But in one sense, the die has already been cast: Ever since the legislation was enacted, Americans’ opinions have been relatively stable, with support never outpacing opposition.

What explains the sustained public disapproval of President Obama’s health-care reform?

For many observers, political rhetoric has been an important part of the answer. Voicing what has become conventional wisdom, former Democratic Senate leader Thomas A. Daschle (S.D.) said: “While we won the legislative war, I think almost from the beginning we’ve lost the message war.”

But if we look at the words that Americans use to explain their support or opposition to health-care reform, we get a different picture — and a different understanding of the importance of anti-ACA messages such as Sarah Palin's invocation of “death panels.”

The Pew Research Center and the Kaiser Family Foundation have both repeatedly asked people to describe why they support or oppose the ACA. Looking at their open-ended answers — with the help of widely used computer algorithm known as Latent Dirichlet Allocation — I identified six groups of words people use to explain their views.

In one such cluster, the four most common words were “cost,” “money,” “pay” and “taxes.” Unsurprisingly, those who highlight such costs are much more apt to oppose than support the ACA.

The same holds true for another cluster, whose most common words included “government,” “control,” “run” and “don't.” Here, we see two central elements of opposition to the ACA: concerns about its cost to taxpayers and concerns about the role of government in the health-care system.

(The words “death” and “panels” are nowhere to be seen, even if the phrase was a stand-in for more generalized opposition to government.)

Click here for a full sized chart.

In the figure above, the six clusters are displayed, showing the frequencies with which supporters (solid black lines) and opponents (red dashed lines) use each set of words.

One of the most notable shifts over time — the chart runs from Obama’s inauguration in 2009 to March 2011 — comes among the supporters, who increasingly adopted language about insurance companies and preexisting conditions. That Democratic message appears to have sunk in.

More generally, though, the relative stability of the survey respondents’ language is striking. Very consistently, opponents talked about two concerns: the ACA’s cost and the increased role of government in the health-care system. They did so beginning in July 2009, before death panels, cloture votes and even Obama’s prime-time address before Congress.

It’s not just that Americans’ overall assessment of health-care reform has been consistent: The very words we use to explain our support or opposition have been steady as well.

With the ACA again taking center stage, we’ll be hearing a lot of strong rhetoric, and many will wonder how that stiff language may shape public opinion. With few exceptions, the data show that the answer is very little. The federal government’s role in the health-care system has been a recurring political issue for generations, and we should be skeptical of the idea that specific rhetorical flourishes will change the basic trade-offs that Americans perceive to be at the heart of the debate.