"The economy, stupid." Democratic operative James Carville used that simple phrase in 1992 to remind former President Bill Clinton to maintain narrow focus on that issue.

Republicans who want to beat Hillary Clinton in 2016 need a similarly single-minded focus: It's the cronyism, stupid.

Hillary is at times a liberal, at times a moderate; here a populist, there an elitist; sometimes a hawk, sometimes a dove; but she's always a crony.

Turn over any rock in Clintonworld, and you'll find some species of cronyism wriggling out from beneath it. Look in her Senate career, and you'll find her selling public policy in exchange for campaign contributions. Peek into the Clinton presidency, and you'll see her husband selling pardons for gifts to his presidential library.

The Clinton Foundation was a breeding ground for cronyism, with new species being bred by the tawdry liaisons of petrol-state money, U.S. corporations, and the former first family. Hillary's brother Tony Rodham, Clinton confidants Terry McAuliffe and Rahm Emanuel — they all occupy this world along with a rogue's gallery of revolving-door lobbyists and public-policy profiteers.

The pervasive cronyism of Clintonism ought to make Hillary very vulnerable in her presidential run — but only if the Republican nominee and the GOP Establishment are ready make an issue of it.

Republicans are often uncomfortable with the cronyism charge. For instance, going after the Clinton revolving door — where senior White House, Senate or State Department aides become corporate lobbyists and then become top Clinton advisers again — strikes a little too close to home for many GOP bigwigs. The upper echelons of the GOP Establishment are populated by the Republican counterparts to these Clinton revolving-door millionaires. They bristle if you use the word "lobbyist" with a negative connotation.

And here's another problem for Republicans: Much of Hillary Clinton's corporatism involves corporate welfare. Until recently, most elected Republicans didn't even like using the phrase "corporate welfare" — it sounded too Ralph Nadery to them.

More to the point, many Republicans practice corporate welfare. For instance: Gov. Rick Perry supports the Export-Import Bank. Gov. Scott Walker has seemingly flip-flopped to support the ethanol mandate. Sen. Marco Rubio supports the federal sugar program. These and similar cases make some Republicans hesitant to attack Democrats' corporate handouts.

But if the task is defeating Hillary, then the cronyism charge is the single best weapon at hand.

When Hillary attacks Republicans for wanting smaller government, point out that her big-government gambits tend to rig the game, profiting her friends and big business donors in ways they could never profit so much in a free market. Point out that her preferred policies enrich the lawmakers-turned-lobbyists and the corporations big enough to afford them.

When Hillary tries to sound populist, saying things like "rich people … do not contribute to the growth of their own countries," the response is easy: "Secretary Clinton, maybe you're speaking from narrow personal experience, because what you said is true mostly of people who get rich off their connections to political power."

The very visible and undeniable fact that Bill and Hillary turned their public service into massive personal wealth is bound to be abhorrent to many Americans, especially swing voters disgusted with a political system that rewards the insiders.

Hillary's deep antipathy toward transparency makes cronyism a more salient issue. Why, as secretary of state, did she try to dodge federal transparency laws and scrub all her email records? What has she been hiding?

Here's one thing she's probably hiding: the cronyism of the Clinton Foundation. Author Peter Schweizer, in his forthcoming book, "Clinton Cash," said that the money trail, as far as we can follow it, reveals "a pattern of financial transactions involving the Clintons that occurred contemporaneous with favorable U.S. policy decisions benefiting those providing the funds," as quoted by the New York Times.

And here's the thing about the cronyism attack: it resonates not only with swing voters, but also with the mainstream media that still acts as a filter. The New York Times, Associated Press, and CBS aren't going to care or notice that Clinton is totally out of line with the middle of the country on late-term abortion, the health-insurance mandate or her support for inheritance taxes. Attack her cronyism, though, and you can sink into the consciousness of the press.

It's a matter of speaking the Left's language — concerns about special interests, the people versus the powerful and a rigged game. Suddenly, the left-leaning media can understand.

This strategy is simple, but that doesn't make it easy. It requires a Republican who's willing to forswear corporate welfare, upset his or her lobbyist friends with some populist rhetoric, and lose some corporate donors. Is any Republican willing to do that?

If not, they're ignoring Hillary's greatest weakness.