That's George Packer's theory:
Karl Rove’s resignation brought to mind a conversation I had a few weeks ago with an Administration official who genuinely wanted to hear my account of why the Iraq war has gone so badly. In a word, I said, “politics.” At every turn, the White House has tried to use the war, and the larger war on terror, to consolidate power, to reward ideological and political loyalists, to win electoral advantage, to push the Democrats into a corner, to divide the country into patriots and defeatists. President Bush insisted on pursuing a highly partisan domestic agenda rather than unite the country around the war in the spirit of F.D.R. (who said that “Doctor New Deal” had been replaced by “Doctor Win the War”). So many disastrous wartime decisions can be traced back to the original sin: policy mattered less than politics. The message in Washington was more real than anything happening in Iraq.
This'd be a kind of fun thing to throw into kitchen-sink style critique of the Bush administration, but I don't think it's very well supported.
For one thing, it lacks explanatory power as an account of White House decision-making over the past 18-24 months. It was widely believed in late 2005 and early 2006 that Bush was going to start some kind of slow-motion downscaling of the American presence in Iraq in order to lessen the extent to which it was a millstone around the congressional GOP's neck, but it didn't happen. Similarly, Bush responded to electoral rebuke not by trimming on Iraq, but by doubling down. The evidence suggests that Bush pursued maximalist Iraq policies in 2002-2005 for the exact same reason he pursued them in 2006-2007 -- because of his maximalist views on Iraq. He was a maximalist when Iraq-as-wedge-issue cut in his favor, and he was a maximalist when Iraq-as-wedge-issue cut against him.
That's not to say that within the parameters of the agreed-upon policy the White House political team didn't try to milk the issue for maximum political advantage, but that's a different matter.
Of course, the question of "why the Iraq war has gone so badly" does admit of a few different interpretations. I would say it went badly primarily because the underlying concept of invading and occupying a diverse, medium-sized country in order to topple a long-entrenched dictatorial regime and replace it with a stable, pro-American one that would be a stepping stone toward larger regional transformation was fundamentally unsound. Any policy designed to achieve those goals was bound to fail. It probably did, however, go as badly as it did ("so badly") in large part because responsibility for implementing this policy was handed over to people who were too dumb, too crazy, or too irresponsible to realize what a mess they were making and abandon the policy objectives.
The notion, however, that if Bush had just made Joe Lieberman Secretary of Defense, not pushed for further tax cuts, invited Paul Berman over for coffee, and given Joe Biden a hug that this all would have turned out well doesn't seem very plausible. Maybe had the administration not disbanded the Iraqi Army, not issued the de-Baathification order, and not made all kinds of noises about marching on Damascus and Teheran we could have installed a stable-but-repressive Sunni neo-Baath regime that made nice with the Gulf Cooperation Council states but liberal hawks wouldn't have been happy with that and I don't think it's clear that it would have worked anyway.