It’s numbers like these that explain why Mr. Obama, who just over a year ago called inequality “the defining challenge of our time,” has lately stopped emphasizing it. Instead he talks about expanding opportunity and mobility. It appears that most voters care more about whether they, and Americans generally, can get ahead than they care about whether they can keep up with the top 1 percent. More evidence for this set of priorities came in the late 1990s, when inequality was rising but middle-class wages were rising, too. The public at the time expressed satisfaction with the direction of the country.

Before taking up a theme that Mr. Obama has largely abandoned, Republicans should consider whether public opinion gave him good reason to abandon it. They should consider, also, whether they can point to any policy proposals of theirs that would do much about inequality. It’s not an accident that economic equality has been a cause traditionally associated with the left. The Democratic drive to increase tax rates on very high earners and on investment income may or may not be wise, but it would probably reduce inequality. The same cannot be said of Republican proposals.

Republicans deride Mr. Obama’s policies for having yielded insufficient economic growth. But if they had policies more to their liking and those policies had generated higher growth, inequality might well be higher as a result. (It tends to rise during high-growth periods.)

Republicans have a few ideas for fighting poverty and taking on what they call “crony capitalism,” the tendency of government subsidies to enrich moneyed interests. Some are good ideas. Relaxing licensing rules that govern who can become a cosmetologist or start a moving company would expand opportunity, and ending corporate welfare would improve economic efficiency. Neither policy, though, is likely to make a dent in inequality. It would be best to argue for them on other grounds.

Republicans are taking up inequality as an issue now for three reasons. It provides a way of attacking Mr. Obama’s economic record even as unemployment rates drop. It gives them an opportunity to deploy rhetoric usually associated with liberals against him and his party. And Republicans have grown increasingly aware, since their defeat in the 2012 election, that their party has a damaging reputation for caring only about the economic interests of the rich.