During the 2012 presidential election, Republicans didn’t consider income inequality a problem, and no one expressed that opinion better than their candidate, Mitt Romney. “You know, I think it's about envy,” he said in January 2012. “I think it's about class warfare.” Instead, Romney focused on opportunity. “I believe in a merit nation, an opportunity nation where people by virtue of their education, their hard work and risk taking and their dreams—maybe a little luck—could achieve great things,” he added.

On CBS’s “Face the Nation” Sunday, former Pennsylvania Senator Rick Santorum criticized Romney for that rhetoric. “I think there's also evidence that [Romney] didn't do a very good job reaching out to the very voters that I just talked about,” he said. “I think there's a lot of folks who are very disenchanted with both political parties because neither party is really talking about them and really saying what's the way forward for the 70 percent of Americans who don't have a college degree but, you know, want economic opportunity like everybody else.”

But for all his criticism of Romney, Santorum doesn't sound much different: Both of their comments were clearly focused on mobility and opportunity. And that makes Santorum an outlier in the Republican field, where others have been unafraid to touch a previously toxic issue on the right: income inequality.

“We’re facing right now a divided America when it comes to the economy,” Senator Ted Cruz said on Fox News after President Barack Obama’s State of the Union. “It is true that the top 1 percent are doing great under Barack Obama. Today, the top 1 percent earn a higher share of our national income than any year since 1928.” Senator Rand Paul had a similar reaction to the State of the Union. “Income inequality has worsened under this administration,” he said. “And tonight, President Obama offers more of the same policies—policies that have allowed the poor to get poorer and the rich to get richer.” Even Romney’s rhetoric has changed to show greater concern about inequality.

And yet, many conservative economists side with Santorum in believing that economic mobility is a more dire problem in America than income inequality.

“Income inequality and economic immobility are often lumped together, but they shouldn’t be,” George Mason University economist Tyler Cowen wrote in the New York Times on Sunday. “Consider the two concepts positively: Income equality is about bridging the gap between the rich and the poor, while economic mobility is about elevating the poor as rapidly as possible. Finding ways to increase economic mobility should be our greater concern.”

Cowen argues that the slowdown in productivity growth over the past few decades is responsible for the meager growth in wages during that period. But as Dean Baker, the co-founder of the Center for Economic and Policy Priorities, notes, the gains to productivity over the past few decades have accrued mostly to the rich. “[I]t is far from clear that inequality does not itself impede productivity growth,” Baker writes. “While it can of course be coincidence, it is striking that the period of rapid productivity growth was a period of relative equality.” Economists think a number of other reasons, including technological change, globalization, and the decline of labor unions, are responsible for the slowdown in wage growth. You can't pin this trend entirely on a lack of productivity growth.

That doesn’t defeat Cowen’s argument that inequality is the lesser concern. Indeed, there isn't overwhelming evidence that a high level of income inequality is, itself, bad for a country. But there is some evidence. Areas with higher levels of income inequality are associated with worse health outcomes, for instance. There’s also growing evidence that high levels of income inequality hurt growth. And the rich gain significant influence over the political process as their money grows.

Like many conservatives who want to dismiss the importance of inequality, Cowen points to “The Equality of Opportunity Project” by economists Raj Chetty, Emmanuel Saez, and others. The landmark study found that mobility in the United States has remained unchanged over the past few decades, even as inequality has increased. Cowen suggests that the mobility stats even understate actual mobility gains because they do not account for the increasing share of Americans who are foreign-born.

But Cowen misses a key point. Last week at the Federal Reserve’s Community Development Research Conference, Chetty wondered why mobility hadn’t increased over the past few decades despite the war on poverty and major decreases in discrimination. Given that, it’s entirely plausible that without rising inequality, mobility would have risen in the recent decades. In fact, rising inequality makes mobility even more important. “When society has huge amounts of inequality,” Chetty said, “it becomes much more important that you have a shot to make it up the income distribution.”

It's quite possible that Santorum isn't immersed in these distinctions and doesn't expect his Republican counterparts—or Hillary Clinton, for that matter—to explore such wonky nuances in their political rhetoric. After all, the right's claim that Obamanomics is increasing inequality is just a desperate attempt to undermine the political gain accruing to the president as the economy improves. Republicans' actual policies—based on a hostility to redistribution and confidence that the free market delivers fair economic outcomes—suggest they don't really care about addressing inequality. Their candidates' economic agendas, at least what we know of them so far, consist of massive tax cuts, targeted largely at the wealthy, and eliminating government regulations. It’s an agenda built for problems of the 1970s, not ones for today.

This isn’t just a GOP problem. In the New York Times last week, Noam Scheiber documented how candidates in both parties are talking a lot about inequality but largely adopting policies that align with the preferences of the wealthy. “Hillary Rodham Clinton, though she has been more open to a government role in solving the problem, has yet to mention tax increases as a possible answer,” he wrote, later adding that she “has also largely avoided saying anything that might offend her wealthy supporters.”

Presidential campaigns are a delicate balancing act between adopting a message that voters can relate to, that donors will approve of, and that solves real problems. So far this cycle, no candidate has found that balance. The Republican candidates’ rhetoric on inequality seems designed to avoid the mistakes that Romney made in 2012, while Clinton's seems designed to conceal where she stands (an approach that may endure through the Democratic primary, barring a legitimate challenge).

And yet, it’s not clear that voters even care that much about income inequality. Romney’s gaffes, like his 47 percent comment, mattered politically not because they ignored inequality, but because they alienated millions of American voters. The same is true of Clinton's gaffe last year, when she said her family was “dead broke” after her husband’s presidency.

So will inequality even matter in 2016? Many political scientists believe structural factors, like the state of the economy and whether the candidate is an incumbent, matter more than campaign messaging. But, as George Washington University political scientist John Sides suggests in Jason Zengerle’s new New York magazine feature on Clinton's candidacy, the presidential election could be very tight; the outcome could hinge on smaller issues, like the media’s treatment of Clinton. But if that's true, then a candidate’s rhetoric on inequality could prove just as decisive.