A shibboleth of the contemporary left holds that the cash tsunami flowing in and around the American political system has eliminated all meaningful distinction between the two major parties. Call it the Tweedle-Dee-and-Tweedle-Dem thesis—the kind of analysis that drives sane people to vote for Ralph Nader (or to stay in grad school).

In his recent book Fortunes of Change: The Rise of the Liberal Rich and the Remaking of America, David Callahan takes aim at this notion, using reams of data to make two ambitious arguments: first, that America’s rich now tilt politically left in their opinions and campaign contributions, and second, despite the surge in corporate funding of Democrats, the Democrats pursue far more liberal economic and business policies than Republicans.

Callahan fully documents that the Democratic Party is much more dominated by huge donations and corporate influence than ever in its history. In the 2008 election cycle, for example, all five of the largest West Coast technology firms whose employees made political donations—Microsoft, Google, Cisco, Oracle, and Hewlett-Packard—gave to Democrats over Republicans by a factor of 3-to-1 or even 4-to-1.

Callahan’s book is brimming with mini-profiles of freshly minted billionaires, from Silicon Valley stars to Greenwich hedge fund machers, who love nothing more than to throw bags of money at Democratic candidates and liberal causes. And he convincingly explains why today’s megawealthy moguls orbit the opposite political planets of their Mad Men-era industrial counterparts. The 21st-century titan has made his fortune not in shabby trades like oil, timber, or wage-slave manufacturing, but rather in sparkling, knowledge-economy fields like law, finance, technology, and entertainment. (This part of Callahan’s book was excerpted in Sunday’s Washington Post.) Hence he (it’s still mostly he) has seen the value of what only government is likely to provide: a well-educated work force; meritocratic immigration policy; speedy infrastructure; and thriving capital markets. The odds are very high that he attended at least university in a liberal-left coastal city, where he learned the good graces of racial and sexual tolerance.

When today’s multimillionaire looks, then, at the public policy arena, he does not carp about high taxes or the encroachment of undeserving classes. The rise of Barack Obama—the super-competent, empathic meritocrat—only fueled the simmering flirtation between today’s rich guys and American liberals.

From that sympathy, Callahan argues, comes the political paradox: The rise in wealthy funding of the American liberalism has not caused a wholesale kowtowing to a corporate agenda. Quite the opposite, says Callahan: “The paradoxical truth of recent years is that the Democratic Party has moved to the left even as its take from financiers has soared.”

Alas, the evidence Callahan offers for this provocative thesis proves primarily that he has spent too much time reading the Almanac of American Politics. That is, his definition of relative leftism relies almost entirely on the ratings produced by various interest groups—such as Americans for Democratic Action and the Natural Resource Defense Council—who score Members of Congress based on their votes on a roster of issues.

That methodology is OK as far as it goes, but it barely goes from Capitol Hill to Union Station. You needn’t peer very deeply into government’s haze to know that when Congress and the Executive Branch want to deliver the goods to corporate America—including specific industries—they do so in cooperative ways that are poorly captured by the tallies of the League of Conservation Voters.

Consider the following, from the last few years alone:

Barack Obama now presides over a trillion-dollar-a-year military budget, the largest in the history of mankind, and as a percentage of American GDP, the largest since the mid-90s.

The deregulation of the finance industry that culminated with the repeal of Glass-Steagall was a bipartisan effort, with Republicans writing the script and Democrats providing the votes.

When the Bush administration tacked tariffs on steel imports to placate the pathetic American steel industry, the only complaint from Democrats was that the tariffs weren’t high enough.

Two free-trade agreements opposed by labor unions (Chile and Singapore) both passed in 2003 with substantial help from Democrats.

Democrats joined Republicans in never making a priority of ratifying the Kyoto Protocol.

Democrats were fully responsible for the failure to pass cap-and-trade legislation during this Congress.

The massive bailouts of Wall Street and Detroit were carried out against public opinion, and very much with the support of corporations, banks, and Democrats in Washington.

The card-check effort for labor unions, not long ago the scariest economic mask the right could force onto Democrats’ faces, has completely evaporated.

I could go on, but the point is clear: Anyone who looks at the last decade and fails to see how moneyed Democrats deliver on the corporate agenda must be myopic. Perhaps today’s limousine liberal cares more about whether his ride is a state-of-the-art hybrid than about the size of the engine—but that’s only because he’s already expensed the rest of the car. If, as Callahan notes, centrist groups like the Democratic Leadership Council no longer have much clout, it’s because they accomplished their major goals—notably the elimination of welfare—and became unnecessary.

And nor should we read too much into the 2008 election. It featured a Republican candidate who was unattractive on many levels, especially his economic ignorance. With Obama alienation currently shared by the left and right, I suspect that the long-term beneficiaries of the demographic forces Callahan describes will be socially moderate Republicans whom Democrats love to support. Callahan notes at one point the overwhelmingly Democratic registration in places like New York City—he says 6-to-1—but seems strangely uninterested in the fact that New York has not elected a Democratic mayor since 1989—by far the greatest GOP domination in New York’s nearly 350 years of voting for mayors. When money dominates the political system, the palatable Bloombergian billionaire becomes its master.

The real message of Callahan’s book is not that the rich have become liberal. It’s that American liberalism itself no longer feels the need to espouse an economic agenda that is decidedly different from that espoused by conservatives. Economics has been surgically removed from the realm of politics and transplanted into a technocratic robot that is run by the Federal Reserve and its acolytes. At least for the time being, most liberal politicians don’t seem to miss it.

Research assistance by Rachel Louise Ensign. Like Slate on Facebook. Follow us on Twitter.