American liberals are notoriously bad at understanding conservative arguments. Donald Trump may be the worst of them all.

The Manhattan billionaire keeps accidentally adopting the positions of Hillary Clinton — whom he has long supported with donations — because he confuses pro-business corporatism with pro-market free enterprise.

Falling behind Ted Cruz in Iowa polls, Trump's comeback strategy is to pander to the Hawkeye State's ethanol bandits and attack Cruz for standing on principle.

In a Des Moines campaign event on December 12, days after the bad polls started pouring in, Trump began his attack: "Where are the ethanol people?" Trump asked the crowd. "with the ethanol, really, [Cruz has] gotta come a long way because he's right now for the oil."

Translation: Trump was attacking Cruz for his plan to wind down the Bush-era ethanol mandate, known as the Renewable Fuel Standard. The RFS forces drivers to use ethanol, a fuel made from plants (mostly corn) by requiring refiners to dilute their gasoline with the stuff.

Clearly anti-market, the ethanol mandate drives up food prices and fuel prices, hurting American families to benefit the special interests in the corn and ethanol industries. It unjustly enriches a small number of people who provide a good that would not otherwise be in demand. Environmental groups also oppose the mandate, which they say degrades soil and water supplies. Also, as Trump alluded, the oil industry dislikes it, because the mandate means more of the gasoline Americans buy is squeezed from corn instead of refined from crude.

The ethanol mandate, like the federal ethanol tax credit before it, exists only because the Iowa caucuses are the first nominating contest. For decades, politicians have sold their souls for ethanol. Al Gore admitted as much, recently explaining his ethanol support was rooted in "a certain fondness for the farmers in the state of Iowa because I was about to run for president."

Iowa winners George W. Bush (2000), Mike Huckabee (2008), and Mitt Romney and Rick Santorum (2012) all supported ethanol subsidies. This time around, most Republican presidential candidates are at least a bit embarrassed by their support. Some, like Carly Fiorina, try to walk a fine line: stating general opposition to the mandate, but saying they won't touch it until the current mandated levels expire in 2022.

Trump is unabashed in his love of corporate corn welfare. He's actually attacking Cruz on it, for one thing. And his love for the ethanol mandate isn't new.

Back in August, when Trump's campaign had only recently taken off, Iowa Gov. Terry Brandstad — whose son is a professional ethanol-subsidy advocate — made it clear that Trump, who frames himself as someone who won't bow to the establishment or to special interests, was in fact bowing to Iowa's special-interest power brokers. "I think he's got a real campaign here," said Brandstad. "Whether he's willing to devote the time ... is the question."

A couple of weeks later, when asked if he would support the RFS, Trump was effusive: "Yes, and a very strong yes," he said. "There's no reason not to. We need it. … Ethanol is terrific, especially with the new process, and I am totally in favor of ethanol, 100 percent. And I will support it."

In November, Trump paid a visit to representatives of the ethanol lobby. As he put it, "I went out to see some of the folks on the ethanol. Good stuff and great people, put a lot of people to work out here. I just want to thank them, they're doing an amazing job."

His full-throated support for the ethanol mandate puts no room between him and Hillary, who has never met a corporate handout she didn't like. It also conforms to the liberal line about conservatives: They say they believe in free markets, but they really just believe in Big Business.

Trump has shown this tendency elsewhere. For instance, he loves eminent domain for corporate gain. He says it's "wonderful" when governments seize property to give it big developers like Donald Trump.

Trump's decision to run on ethanol welfare is clearly a naked pander to Iowa special interests, but that's not the entire story.

When considered together with his love of eminent domain to benefit developers, it reflects Trump's view of capitalism, which is also the liberal stereotype of the capitalist — that he simply wants what's best for the rich and successful.

It's almost as if Trump isn't a real conservative.

Timothy P. Carney, The Washington Examiner's senior political columnist, can be contacted at tcarney@washingtonexaminer.com. His column appears Tuesday and Thursday nights on washingtonexaminer.com.