The span of time between candidate George H. W. Bush's "read my lips, no new taxes" pledge, and his subsequent decision as president to break his pledge by supporting new taxes, was approximately two years. John McCain has now managed to violate that same pledge in just 20 days.

Here's the straight-talker's recent track record: Back on July 7, he told an audience: "Barack Obama will raise your taxes. I won't." More specifically, McCain economic adviser Douglas Holtz-Eakin said on June 13 that the candidate would refuse to raise the Social Security payroll tax "under any imaginable circumstance."

More generally, McCain told Fox News on March 16 that he would try to cut taxes whenever possible, and never raise them. Host Sean Hannity pressed him on that pledge and asked, "None?" And McCain replied, "None."

More specifically again, when conservative commentator Ramesh Ponnuru asked McCain in March 2007 whether there were any circumstances, during negotiations over entitlement reform, that would compel him to accept a tax increase, he replied, "No, no." Ponnuru pressed him: "No circumstances?" McCain replied, "No. None. None."

And more generally again, McCain told ABC News on Feb. 17 of this year: "No new taxes...In fact, I could see an argument, if our economy continues to deteriorate, for lower interest rates, lower tax rates."

Cut to McCain's appearance ABC this past Sunday. During a discussion about the future of the Social Security program, McCain was asked whether he'd consider a hike in payroll taxes. His reply: "There is nothing I would take off the table." When host George Stephanopoulos asked, "So that means payroll tax increases are on the table as well?," the candidate again said: "Nothing's off the table. I don't want tax increases...But that doesn't mean that anything is off the table."

Democrats like to link McCain to President Bush (often, for valid reasons), but, in one important sense, the two men differ greatly. Bush was a famously disciplined candidate, resolutely on message. But McCain? This guy is all over the place, stepping on his own alleged convictions, and - particularly in the instance cited above - infuriating his own conservative base. The same base that, according to all the polls, is insufficiently galvanized by his candidacy with just 99 days remaining on the election clock. And sure enough, one of the prominent ant-tax groups, the Club for Growth, fired off a letter to McCain yesterday (while emailing it, naturally, to the press), complaining that his "shocking" Sunday statement on ABC has sent "a mixed message about where you stand on this issue."

But by now the conservatives are probably aware that McCain will often flop-flop in their direction as well. In that same Sunday interview, he blatantly reversed himself on another issue, leaving behind a "maverick" stance that he took a decade ago and moving rightward with nary a look back at where he stood before.

First, the history: Back in 1998, there was a ballot initiative in his state of Arizona that was designed to end affirmative action. McCain opposed it at the time, dismissing it as "divisive." But apparently he was against it before he was for it, because this year a similar initiative is on the Arizona ballot, and when he was asked on ABC whether he supports it this time, he replied: "Yes, I do. I do not believe in quotas. But I have not seen the details of some of these proposals. But I've always supported quotas."

The biggest problem with this particular flip-flop is McCain's ill-informed explanation. The Arizona ballot initiative is not about quotas at all (it simply states that public institutions should not "grant preferential treatment to any individual or group on the basis of race, sex, color ethnicity, or national origin..."), and, indeed, quotas have generally been barred by the U.S. Supreme Court as far back as 1978. So McCain is raising a phony issue - which is not surprising, since he admits that "I have not seen the details" of the issue he is purporting to discuss.

Indeed, not even McCain's spokesman was able to sort it all out the other day; when Tucker Bounds was asked to square McCain's previous opposition to an affirmative action ban with his new support for an affirmative action ban, he didn't even attempt to spin: "I do not have a firm enough grasp on the historical and relevant context of McCain's remark in 1998 to give you the pushback that this question deserves."

It's possible that McCain was talking off the cuff, with no memory of where he had stood before; more likely, he was deliberately pandering to the base on a pet conservative issue, in the hopes of demonstrating that he's not such a maverick after all, that he's willing to toe the line even at the risk of further alienating minority voters and perhaps jeopardizing his outreach efforts to women (who, after all, have been helped by affirmative action, particularly with respect to recruitment programs).

All told, these two flip-flops (one currying favor with the right, the other risking anger on the right) are prime examples of McCain's delicate, and sometimes clumsy, attempts to stoke his base while seeking some distance from its dictates. This balancing act puts his "straight talker" image at dire risk, although I suppose that if one takes whatever he says in the moment as gospel, and ignores whatever he said on the same subject at an earlier date, he will always look every inch the resolute leader that he purports to be.