It's no secret that the corporate class is being eclipsed by Tea Party libertarians and is increasingly unable to exert influence on the Republican Party, despite the generous donations the top 1 percent has long showered on Republicans.

But isn't the Republican Party in the business of serving Big Business? And didn't the Supreme Court ruling in Citizens United open the floodgates of corporate campaign cash? How is all that corporate campaign cash failing to buy Big Business sway over the GOP?

Well, here's the thing: Citizens United didn't save the Republican Party. Citizens United broke the Republican Party.

Yes, Citizens United was what Republicans and their corporate patrons wanted. Corporations are people. Money is speech. Spend what you want, and no one needs to know who wrote the check.

But as conservative columnist Tim Carney explains in a criminally overlooked Washington Examiner column from last month, what Citizens United meant in practice is this: It "spawned super PACs that offset the power of the political parties and K Street."

Carney specifically credits the newly created Senate Conservatives Fund and Heritage Action groups for using the new post–Citizens United rules to fund right-wing challengers who have triumphed over Republican establishment favorites, whipping up conservative grassroots fervor behind extremist positions and forcefully shaming any Republican who hints at compromise. They have their own informal "whip operation" that robs Speaker John Boehner and Senate Minority Leader Mitch McConnell of their traditional institutional power. And they have been squarely behind the plot to defund ObamaCare by forcing a government shutdown.

Carney says this Citizens United–fueled dynamic has led to a "Republican leadership vacuum." I would go a step further: It has broken the Republican Party in two.

Both the ascendant Senate Conservatives Fund and Heritage Action groups are financially backed by the libertarian billionaire Koch brothers, leaders of a single corporation that appears to be trying to surpass the Chamber of Commerce as the dominant funder and power center of the Republican Party.

In the 2012 elections, the Chamber of Commerce and the Koch-backed Americans for Prosperity each spent roughly $35 million. But since then, the Kochs have used another group they created, Freedom Partners Chamber of Commerce, to spend $200 million supporting an array of organizations determined to destroy ObamaCare.

According to Open Secrets, Freedom Partners Chamber of Commerce spending now "dwarfs" the old Chamber, which has been urging Republicans to keep the government open and increase the debt limit, to no avail. The establishment Chamber has become so frustrated with being ignored, it is preparing an effort to donate money to Republican congresspeople who face primary challenges from the right, a direct challenge to the Senate Conservatives Fund and its allies.

The Republican Party is stuck with two major corporate funders vying for influence and pulling the party apart. Yet the organization with the broader business base and more rational political outlook is being out-organized and out-spent by a narrow band of ideological extremists who have figured out how to best exploit a Citizens United world. Recent research has found that Citizens United did not entice corporate America en masse to increase its election spending, but as The New York Times's Eduardo Porter noted, "Big, frequent donors are particularly extreme."

The end result is a party compelled to carry out a doomed legislative strategy concocted by the party's most aggressive funders. If fully carried out to its apocalyptic conclusion, the strategy risks obliterating the Republican Party's brand for a generation.

Just one year ago, Democrats were terrified that Citizens United would not only drown Barack Obama in a flood of GOP-friendly corporate cash, but also make it impossible for liberal Democrats to ever have a chance at winning national elections.

But the reverse may end up being Citizens United's true political legacy.

Obama used the specter of freshly legalized super PACs to rev up his donor base, and raised more money than any presidential candidate in history, neutralizing the Republican super PACs. He kept his party unified, turned out his base, and won decisively. In the election's aftermath, well-funded but strategically inept right-wing super PACs are financing deep intraparty discord, threatening the ability of Republicans to be competitive in national elections.

Turns out the upholding of the Affordable Care Act isn't the only gift Chief Justice John Roberts gave to President Obama.