And they won't want to hear it; won't listen.

Perhaps. But it's equally true that a very large portion of his party really doesn't believe in free trade, immigration to meet business needs, government austerity, or free market maximalist withdrawal from national industrial policy.

Right-wing populism is an answer to "What's the Matter With Kansas?". Instead of socially conservative, economically liberal working class voters deciding to ignore the cultural red meat thrown at them by the GOP's business elite and vote Democrat, they instead decided to just throw the GOP's business elite faction out of power and elect protectionist and immigration hawk Republicans that don't want to cut Social Security or Medicare.

For obvious reasons, Romney prefers to emphasize his disagreement with the "not believe in the Constitution" part of populism. But a very large portion of his party now rejects a number of foundational substantive positions that his faction of the party supported.