Daniel Patrick Moynihan – four-term U.S. senator from New York, ambassador and White House adviser – was that rarest of combinations: a gifted public intellectual and a talented, practical politician.

He alone, in January 1980, during the depths of the Cold War, dared to say, “The defining event of the decade might well be the breakup of the Soviet empire.” On Nov. 9, 1989, the Berlin Wall came down.

Pat Moynihan also had a wicked sense of humor. At Washington’s annual Gridiron Club dinner on March 28, 1981, with President Ronald Reagan sitting not 10 feet away from him, Moynihan told the crowd how David Stockman, the president’s controversial boy-wonder budget director, had, as a graduate student, been the Moynihan family’s live-in baby sitter. Young Stockman, according to Moynihan, railed endlessly against “American imperialism and the immorality of the Vietnam War.”

Moynihan continued: “So we installed him in the top floor of our house and got him into the Harvard Divinity School. There he was taught, of course, that there is no such thing as morality.”

Moynihan then “confided” to the dinner crowd and Stockman’s boss that “Dave was everything you could dream of in a mole,” that Stockman had been programmed to sabotage the Republican revolution from within by running up record-shattering budget deficits, thus swelling the national debt and destroying any Republican claim to fiscal responsibility.

Do we not know that if Moynihan – who departed these earthly precincts in 2003 – were still here, he would have, long ago, sounded an eloquent alarm on the Republican presidential front-runner, real estate billionaire Donald Trump, and identified him for what he obviously is, a Democratic mole?

Look at what the maverick front-runner has already done to subvert the party where there had previously been, at the presidential level, overwhelming consensus – for example, on the virtue and value of free trade. Trump inconveniently has pointed out how the U.S.’ trade deficit with Mexico increased more than fiftyfold in the first 15 years of NAFTA and has insisted on ignoring the big picture of increased “economic growth” while harping on the American jobs that have been sacrificed to foreign competition and on the people who lost those jobs and their hometowns.

The only nonnegotiable unanimity among contemporary Republicans is found in the party’s uniform opposition to any increase in taxes. So what has Trump done? He has spouted heresy, saying he would be “OK with” raising taxes.

He, of all people, wants to punish success. Of big earners in hedge funds, he has said: “They make a fortune. They pay no tax. … The hedge fund guys are getting away with murder.” Yes, he would even “take carried interest out” (referring to the preference that taxes hedge fund and private equity income at only about 20 percent). This man is clearly a Democratic plant, subversively but brilliantly undermining the Republican Party by smashing party consensus while rising to the top of polls of party members.

All this is not to mention Trump’s immigration position, which has effectively driven voters who are themselves or who have family or loved ones who are immigrants away from the GOP and into the open arms of the Democrats. Ronald Reagan was the man who put a smiling face on American conservatism, and Donald Trump could be the man who puts a pouty face on this year’s conservatism. Pat Moynihan would have warned us months ago: Donald Trump is obviously a double agent for the Democrats bent on sabotaging Republican hopes for 2016.

Editor’s note: To find out more about Mark Shields and read his past columns, visit the Creators Syndicate website at www.creators.com.