Rick Santorum announces he will seek the Republican presidential nomination at Penn United Technologies Inc. in Cabot, Pa., on Wednesday. (Andrew Harrer/Bloomberg)

RICK SANTORUM officially entered the GOP presidential race Wednesday, pitching himself as an economic populist in touch with working-class voters suspicious of both “big government and big business.” So his candidacy may test how strong populist sentiment has become among the Republican rank and file — if, that is, he is seen as anything more than the Christian moralizer he has become famous for playing.

Mr. Santorum has been among the sternest of culture warriors over the past three decades. His most notable legislative accomplishment in 12 years in the Senate was shepherding a bill that banned late-term abortions. He also successfully pushed restrictions on “fetus farming” for research or medical purposes. Part of his breakthrough in the 2012 GOP contest owed to his frank discussions about raising a child with a life-threatening disability; he brought her onstage Wednesday. He stresses the importance of family, pointing out that government can’t read bedtime stories to children. Yet just as often he strikes a sour note, as when he recently said that he wouldn’t attend a gay wedding.

Mr. Santorum will face strong competition from Ted Cruz, Mike Huckabee and others for the evangelical Christian voters who propelled his 2012 campaign. He is therefore emphasizing his sympathies with working-class voters. “Ladies and gentlemen, this is a piece of coal,” he said Wednesday, brandishing a chunk of black rock and explaining that his grandfather worked in the mines after fleeing fascist Italy.

In his campaign book, “Blue Collar Conservatives,” Mr. Santorum argues that the GOP needs to woo “middle- and lower-middle-income Americans from industrial and rural communities with generally conservative values,” millions of whom stayed home in 2012. These “blue-jeaned workers,” he says, “have been left behind and see little hope for the future.” He supports raising the minimum wage and criticizes other Republicans’ preoccupation with cutting taxes for the wealthy.

Neither of these positions is outrageous. But they, along with seemingly everything else Mr. Santorum believes, emerge from a backward-looking traditionalism that esteems an imperfect past and condemns the reforms of the past several decades. “Dramatic, dangerous changes are taking place in America,” he hyperbolically warns in his book, in which he laments the erosion of the U.S. manufacturing economy and the “coarsening” of society. “The greatest threat to the average American’s achieving his dream today is a dysfunctional culture,” he insists. This line of thinking dismisses the progress of recent years, such as on gay and lesbian rights, and encourages overheated attacks on globalization and free trade.

For now, Mr. Santorum’s pitch doesn’t seem to be resonating, either because it’s not what rank-and-file Republicans want or because they don’t believe he is the best exponent of these values. He might not even make it into the first GOP debate, scheduled for August, which will exclude candidates without decent poll numbers. He surprised many when he won 11 primary and caucus states in 2012. If his aggressive, populist touch works as well in the competitive 2016 environment, it will be far more unexpected.