Skeptics voted heavily Democratic in 2012, but they seem perhaps the Democratic type that could be most open to Republican overtures (though I think gains could be made in the Faith and Family Left, too).* Olson suggests that winning over this group would demand at least understanding its worldview:
Winning the support of blue-collar voters means gaining their trust, and that means first affirming the core elements of their worldview. They have to believe that the GOP nominee understands that they have been the losers in the transition to a modern economy. They have to believe that the nominee will be on their side when the chips are down and that he is willing to take on the powerful.
Gaining among Skeptics, Olsen suggests, could require policy reforms for immigration, taxation, and other issues.
As this Washington Post story hints, some Republican presidential candidates are coming around to the understanding that, to win in November, the GOP nominee will have to be able to appeal to working-class voters. One of the underlying arguments in the 2016 primary has been about whether and how to make this appeal.
*And, obviously, Republicans should try to offer an inclusive, expansive message that could win a variety of voters.