Liberals have long repeated the self-assuring myth that the Tea Party, broadly understood, is just a spasm by corporate interests that have always been Republican. John Nichols at the Nation asserts that there is basically no difference between Mississippi Sen. Thad Cochran and his Tea Party challenger Chris McDaniel, who now appear headed to a runoff in their primary.

Nichols sets up a straw man and knocks it down thus:

McDaniel is a conservative.

And so is Cochran.

Despite the theater-of-the-absurd campaign, it is even more absurd to suggest that Cochran is a liberal with a southern accent. Mississippi is not in the habit of populating the Senate with progressives. The incumbent’s latest U.S. Chamber of Commerce rating is 100 percent, while his National Education Association ranking is 0.

I assume Nichols is really referring to the Chamber's 2012 scorecard, which Cochran aced. But here's the point that's mostly lost on liberals like Nichols: The most conservative Senators didn't get a 100 percent in 2012. Mike Lee, Jim DeMint, Rand Paul, and Pat Toomey were 6-for-8 as compared to Cochran's 8-for-8. They clashed with the Chamber on reauthorizing the Export-Import Bank, a corporate welfare agency beloved by President Obama and the Chamber, but opposed by Republicans who believe in free trade.

The other issue where Cochran and the Chamber sided against conservatives was the massive highway bill.

You see, sometimes there's a difference between being a conservative and being pro-business. Cochran is generally conservative, but more consistently, he's pro-business. The Tea Party types are often pro-liberty despite what the business lobby says.

If the policy distinctions here are too hard to see, look at the donor rolls.

The Club for Growth spent a little over $2.8 million backing McDaniel, while the Senate Conservatives Fund spent $1.3 million for the cause, and FreedomWorks and some other groups poured on a bit more.

The Chamber of Commerce spent $500,000 backing Cochran. A PAC called "Mississippi Conservatives," funded by some big businesses and wealthy investors, spent $1.7 million for Cochran. The National Association of Realtors and the Obamacare-backing American Hospital Association also spent significantly to help Cochran.

Cochran's actual campaign committee dramatically outraised McDaniels, with the difference driven mostly by cash from corporate PACs.

All of this money looks the same to liberals, I'm sure: It's all rich conservative businessmen. But there's a difference.

First, much of the pro-McDaniel Tea Party money is small-dollar, grassroots conservatives--the type of people who show up in tricorner hats.

But the big-dollar pro-McDaniel money — say, the Club for Growth's big donors — is different from the big-dollar pro-Cochran money. The difference is ideological money versus pragmatic money:

Rich libertarian investors on McDaniel's side. Rich Republican lobbyists on Cochran's side. People who want smaller government because they believe it's best versus people who want flexible Republicans elected -- either because it profits them, or because they're just loyal to the GOP.

This has been the split in the GOP since the bailouts: K Street versus the Tea Party. Acknowledging they are different is crucial for anyone trying to give an honest assessment of the political landscape. But acknowledging the difference is difficult for anyone trying to write off free-market arguments as corporate shilling.