Earlier this month, I noted that Alison Lundergan Grimes, the Democrat running against Mitch McConnell in Kentucky, was, intriguingly, elevating an issue that one doesn't hear Democrats elsewhere talking up nearly as much as they should: raising the minimum wage. Grimes stressed that plank both in her introductory video and in the speeches I saw her give in western Kentucky on the weekend of the annual Fancy Farm political festival. The choice of issue was particularly striking given that Grimes is nobody's idea of a raging liberal—she's skeptical of Obamacare and dead-set against the Obama administration on coal policy. But she seems to have calculated that calling for raising the federal minimum wage—now $7.25—is a winner in a state with more than its share of low-wage workers.

Well, now (courtesy of a heads up from my colleague Nate Cohn) comes more data to back up her calculation, and to further press the question of why other Democrats are not following Grimes' lead, especially as the plight of low-wage workers gains more and more attention nationwide. A new article out from the Pew Research Center suggests that there are few issues better designed to split the GOP coalition than the minimum wage. The article notes that a February survey question on raising the minimum wage to $9 found:

Overall, Republicans are evenly divided over raising the minimum wage (50% favor, 47% oppose). By contrast, large majorities of Democrats (87%) and independents (68%) support the minimum wage hike. Within the GOP base, there are sharp educational and income differences over increasing the minimum wage. Six-in-ten (60%) Republicans and Republican-leaning college graduates oppose the proposal, while about the same percentage of Republicans who have not completed college (58%) favor it. Higher-income Republicans (those with family incomes of $75,000 or more) oppose a minimum wage hike by 57% to 40%. Republicans and GOP leaners with incomes of below $30,000 support it by about two-to-one (68% to 31%).

Liberals have spent years now agonizing over why it is that many working-class white Americans vote for the party whose policies on taxes, organized labor and much more work against their own ecomomic interests—the "What's the matter with Kansas" problem. Well, here is an issue where lower-income people who vote Republican are quite clear about what's in their own interest—that is, they state a preference at direct odds with their party's line. Maybe it would be a good idea for Democrats to try to peel them away by actually talking up that issue?

Giving even more credence to the notion that Grimes and other Democrats should be targeting their message more toward downscale voters with this issue is exit polling from the last big race in Kentucky, Rand Paul's 2010 victory over Jack Conway. Paul won easily in that year of the GOP landslide, with 56 percent. But Conway won by five percentage points among voters with incomes below $30,000. Granted, many of those were African-Americans. But far from all of them were—Kentucky's black population amounts to only 8 percent of the state's total. Two years earlier, the Democratic challenger to McConnell won an even larger margin among voters under $30,000 income, with close to 60 percent of the vote.