A strategy often employed by southern republican politicians by which promises of reducing minority crime, welfare cheaters, and illegal immigrants reel in the support of low income white voters. This strategy thinly veils a racist agenda on part of the politician in that it plays into the fears of the public of minority groups. In the time of the civil rights movement Nixon often used this strategy to subvert support for the black community, and in subsequent years Reagan used this strategy as well. Most recently, Donald Trump used this strategy to gain popularity with the southern population.
This link gives a nice timeline and clear explanation of the southern strategy