The hot topic in American politics is President Trump’s bid to win black voters away from the Democratic Party. His campaign ran a Super Bowl ad touting his signature on a bill that helped a black grandmother get out of federal prison; during his State of the Union address, the president boasted that African American unemployment has never been lower and presented a series of black beneficiaries of his policies.

Will it work? Consider this ingenious experiment that social scientists conducted late in the 2012 presidential campaign.

Pairs of African American students were given $100 each and told that they could donate either to President Barack Obama’s campaign or to that of his opponent, Republican Mitt Romney. They were also told they could keep $1 for every $10 they gave to Romney.

Each time, though, one of the two students, secretly cooperating with the social scientists, announced that he or she intended to give entirely to Obama. Thereupon, the other student did so as well, forfeiting an easy 10 bucks.

Conclusion: Black Americans are such loyal Democrats, and voting for Democrats is such a powerful norm in the African American community, that you literally cannot pay black people to “defect” openly.

These and other data appear in a provocative new book, “Steadfast Democrats: How Social Forces Shape Black Political Behavior,” by political scientists Ismail K. White and Chryl N. Laird. They argue that peer pressure — or “racialized social constraint” — is a key determinant of African American partisanship.

To be sure, most black Americans vote Democratic because they prefer that party, and what it stands for, over the Republican Party. Yet a significant minority of African Americans — nearly a third, White and Laird report — consider themselves conservative and share at least some Republican economic and social positions. It is on this segment of the black electorate that intragroup social pressure primarily operates, causing many to back Democrats, the authors argue.

White and Laird’s analysis superficially supports the right’s complaint that coercive group dynamics confine black people to a “Democrat plantation,” in pro-Trump black activist Candace Owens’s derisive phrase.

Actually, as White and Laird astutely note, racialized social constraint is a rational, and indeed natural, strategic response to the collective-action problems any minority group faces in a majoritarian political system.

To the extent that individual black people’s survival and progress depend on the group’s ability to leverage its power — and during slavery, segregation and the civil rights revolution, that was a large extent — it makes sense to preserve unity and deter “free-riding.”

“None of the basic social or psychological mechanisms . . . are particularly unique to African Americans,” White and Laird write.

Unions brand non-dues-paying workers “scabs.” Southern whites may be using their own form of racialized social constraint now to enforce pro-Trump Republican voting, the authors suggest. Note the herdlike pro-Trump behavior of Republican senators.

Obama, uniquely popular among black voters, is not on the ballot in 2020, so the 2012 experiment does not apply simplistically to this year.

Trump’s strategists sense an opening to exploit economic self-interest — promoted by pro-Trump African American spokesmen such as musician Kanye West and Republican Sen. Tim Scott (S.C.) — and break through the social network effects that have caused some blacks to stick with the Democrats despite having a more conservative ideology.

It’s a brazen gambit, given the president’s vicious personal attacks on not only his predecessor, Obama, but also other black Democratic icons such as Reps. John Lewis of Georgia and Elijah E. Cummings of Maryland (who died in October).

There is a certain “so-crazy-it-just-might-work” quality to it, however. All Trump has to do to help his cause in swing states is increase his 8 percent national support among African Americans in 2016 by a couple of percentage points, or persuade a significant number of black voters to sit out the contest.

“What he was saying to African Americans can be effective,” Democratic commentator Van Jones, who is black, warned on CNN after the State of the Union address.

Laird is skeptical. Though America is much less segregated than it was 50 years ago, she told me in an interview, black citizens still generally live in “predominantly black spaces, where there is enforcement of a group norm in terms of partisanship.”

As her book points out, would-be African American Trump voters still face the following choice: cast a secret ballot for Trump and admit it later to friends and family, taking heat at church or school; or conceal it, preserving social relationships but creating internal psychological distress.

“Given the social rewards of conformity, voting Democratic is the least costly option,” White and Laird write.

It would probably take a dramatic increase in neighborhood integration to change these dynamics. But the GOP’s white Southern base is not exactly clamoring for aggressive federal housing desegregation policies. In fact, the Trump administration rolled back the initiatives Obama took.

It’s not easy to get people’s votes while signaling that you don’t want them living next door.

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