It's big business versus the free market once again as K Street lobbyists square off against Tea Party groups in two Republican House primaries this spring.

Moderate Republican Mike Simpson is fighting to hold onto his Idaho seat as the Club for Growth spends big to unseat him. Meanwhile, some business interests are bankrolling their own challenger in Michigan, targeting the rebellious libertarian-leaning Republican Justin Amash.

Follow the money, and you see a pattern: lobbyists and corporate PACs backing the moderate, and the Club for Growth backing the conservative.

The bloodiest fight between the business lobby and the Club for Growth is in Idaho, where the Club is backing Bryan Smith in a primary challenge to Simpson.

Simpson is an eight-term congressmen with a lifetime Club voting record of 57 percent — that’s worse than 200 of his Republican House colleagues, and he represents a conservative district.

The Club blasts Simpson for supporting the Wall Street bailout, earmarks and generally big budgets. None of these things, of course, bother K Street. And it shows in the Federal Election Commision reports.

Not a single business PAC, lobby group or lobbyist has given to Smith in the past six months, my search showed.

Simpson, meanwhile, is swimming in K Street cash. He’s raised more than half a million from business PACs, including plenty with some lobbying priorities one could hardly call “free enterprise.”

Simpson's vote for the 2008 Wall Street bailout is the first charge in the Club for Growth's indictment of him. Bailout recipients General Electric and Goldman Sachs are on Simpson's long list of PAC donors.

Simpson supports one of the least defensible federal corporate welfare boondoggles -- the sugar program, which drives up costs for food makers and consumers while enriching a few sugar growers. Seven different sugar-industry PACs have donated to keep Simpson in office.

The PACs of some of K Street's most prominent firms also turn up on Simpson's donor list, including Baker Donelson, DLA Piper, and Dickstein Shapiro. And the U.S. Chamber of Commerce is currently spending $250,000 on ads for Simpson.

The Club for Growth — funded largely by libertarian and conservative business owners — has bundled $300,000 for Smith's campaign and has spent nearly half a million on ads.

The same fight is unfolding on a smaller scale in Grand Rapids, Michigan.

Local businessman Brian Ellis has pocketed $16,000 from business PACs since entering the race against Amash last October. In that same period, Amash has outraised Ellis overall, but he has taken in about one-third as much from business PACs: $4,000 from Koch Industries, $1,000 from Delta Air Lines, and $500 from the K Street firm DLA Piper.

DLA Piper is home to the only two K Street lobbyists whom I could find supporting Amash since Ellis entered the race: Tom Korologos (who is Greek Orthodox, like Amash) and George Salem.

Ellis, meanwhile, has a platoon of K Street donors. Mark Valente, a Michigan native, founded the downtown D.C. lobbying firm Valente partners. Valente hosted a fundraiser for Ellis and, together with his wife, has given about $4,900 to the Ellis campaign, according to FEC filings.

Ellis donors also come from lobbying firms Greenberg Traurig, Ferguson Strategies, and Navigators Global. Between lobbyists and corporate PACs, Ellis has taken in three times as much money from K Street as Amash since October 2013.

Almost half of the $830,000 raised by Ellis is a personal loan to himself. Of the rest, only 3 percent is from small donors. Amash has raised 20 percent from small donors.

Amash doesn't lack for big money backers, though. The Club for Growth has spent more than $195,000 in independent expenditures supporting him, and has bundled more than $190,000 in donations.

Amash adheres strictly to his libertarian principles and the text of the Constitution. Andrew Johnston, political director of the Grand Rapids Chamber of Commerce, finds this annoying. “There is frustration among those who think his rigidity make it difficult to move forward on legislation," Johnston said in the Wall Street Journal.

Ellis also has no patience for Amash’s insistence on abstract ideas like the Constitution and liberty. “He’s got his explanations for why he’s voted,” the Weekly Standard quoted Ellis saying, “but I don’t really care. I’m a businessman. I look at the bottom line.”

You often hear this no-nonsense, pragmatic talk from the “pro-business” side of the GOP. It's supposed to be a virtue. But often it means obeisance -- or at least deference--to special interests.

Ellis may have the local business establishment behind him, but because he’s challenging an incumbent, he doesn’t have the full K Street GOP establishment behind him. Of course, neither does Amash.

K Street versus the Tea Party is the main divide in today's GOP. Idaho and Michigan will help determine who has the upper hand.

CORRECTION: Club for Growth spent $195,000 in independent expenditures in support of Rep. Justin Amash. The dollar figure was incorrect in an earlier version of this column. The Washington Examiner regrets the error. This column was originally posted at 6:06 p.m. April 22 and was updated at 9 a.m. April 23.

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