When the Republican Party deviates from its limited-government talk, it's almost always at the bidding of Big Business. And in these cases Mississippi Sen. Thad Cochran almost always sides with Big Business.

Cochran, the six-term Mississippi senator, has suddenly become the underdog in his re-election. The Republican primary has gone to a runoff after Cochran and conservative challenger Chris McDaniel both finished with 49 percent of the vote. (McDaniel finished 1,386 votes ahead of Cochran.)

McDaniel has succeeded thanks to grassroots enthusiasm and $3.6 million in support from the Club for Growth and Senate Conservatives Fund. Cochran has survived so far on the strength of $500,000 from the Chamber of Commerce, $1.6 million from political action committees (mostly business PACs), $1.7 million from a business-funded super PAC called Mississippi Conservatives, and more than $100,000 in contributions from lobbyists.

Go through Cochran's PAC checks, and you see many clients of the corporate welfare Cochran supports.

The PACs for the Florida Sugar Cane League, the Michigan Sugar Company, the American Sugar Cane League, and nine other sugar PACs contributed a combined $40,500 to Cochran’s primary this year, according to his mid-May federal filing.

Cochran consistently champions the sugar industry's top lobbying priority: the federal sugar program, which drives up prices for American families and food makers in order to enrich a handful of sugar growers and refiners.

The federal government drastically limits U.S. imports of sugar, leaving Americans with a higher price for sugar than the rest of the world pays. At the same time, through a boondoggle “loan” program, the U.S. Department of Agriculture pays farmers 22.9 cents a pound for any sugar they don't sell. To keep that sugar off the market (and thus to keep sugar prices high), USDA then turns around and sells that sugar to ethanol producers for a nickel a pound, or less.

Conservatives often try to kill the sugar program. Cochran always defends it. In 2001, for instance, Sen. Judd Gregg, R-N.H., proposed an amendment to that year's farm bill to phase out the sugar program. Cochran voted to kill Gregg's amendment. In 2012, 30 Republicans voted to kill the sugar program--Cochran voted to save it. Compromise efforts in 2012 and 2013 garnered a majority of Senate Republicans, but Cochran opposed reform both times.

Aside from the sugar program, the least defensible bit of federal agriculture corporate welfare is probably the constellation of ethanol subsidies. One of the top donors to the Cochran-supporting Mississippi Conservatives super PAC is Ergon, an energy company with an ethanol subsidiary.

The Republicans' 2005 energy bill created the federal ethanol mandate, which basically forces the plant-based fuel to be mixed with gasoline. In that debate, Cochran voted in favor of the mandate. In 2011, Cochran split from most of his party and opposed the effort to end the ethanol tax credit. That same year, John McCain tried to end federal subsidies for ethanol storage facilities and blender pumps, and Cochran voted to keep them.

Cochran's fondness for corporate welfare goes beyond the farm.

At every chance, Cochran has voted to reauthorize the Export-Import Bank, the federal agency that subsidizes U.S. manufacturers. Cochran's PAC donors include plenty of Ex-Im's largest clients--General Electric, Boeing, and Caterpillar, for instance.

Cochran voted for the mortgage bailout in July 2008 -- the so-called “Bank of America Bill” -- and the Realtors PAC and the American Bankers Association PAC have funded Cochran's re-election.

Back in 2003, Cochran voted to expand Medicare to cover prescription drugs, helping pass a bill heavily supported by the drug and health-care lobbies--both of which are helping him in his difficult re-election.

Two notable exceptions to Cochran's corporatist streak: In 2008 Cochran voted against the great Wall Street bailout and the bailout of the automakers.

Also, when Minority Leader Mitch McConnell whips his caucus to oppose President Obama's corporate welfare, Cochran obeys--he opposed the 2009 stimulus, for instance.

In general, though, the rule holds: When Big Business and free markets clash, Cochran sides with Big Business.

This is the main Republican divide today: the Tea Party versus K Street. K Street still has a pretty firm grip on the party, but the fact that the business lobby even has a rival for control of the GOP is something new.

There's no doubt the business lobby wants to keep Thad Cochran in the Senate. Sadly for Cochran, corporate PACs don't get to vote in the runoff.