President Obama has discovered that his GOP rival, former Massachusetts Governor Mitt Romney, is a known flip-flopper. "Now that we're 18 days out from the election," Obama said at a speech on Friday, "Mr. 'Severely Conservative' wants you to think he was severely kidding about everything he said over the last year," the president said. "He told folks he was the ideal candidate for the Tea Party, now he's telling folks, 'What? Who me?' He's forgetting what his own positions are. And he's betting that you will too."

The president, who went on to diagnose his rival with "Romnesia," is of course right that Mitt Romney has displayed an impressive capacity for flip-flopping. As I argued in my March feature on Romney, the former Massachusetts governor has altered his position on nearly every major political issue of the day, from immigration to gun control to carbon-emissions policies to abortion. Romney's continuously adjusting positions are one of the biggest reasons that many people say they do not trust him. At minimum, they make it hard to confidently guess what he might do as president.

But consistency has not always been the president's strong suit either. From time to time he has straightforwardly reversed himself — explicitly flipping his position, for example, on the individual mandate to purchase health insurance, which he campaigned against in 2008, and later alternately declaring that the mandate both is and is not a tax.

Most of the time, however, Obama's reversals have taken a different form. Rather than openly reversing himself like Romney, Obama declares his position on a matter, fails to follow through with actions that support that position, and then when questioned about it insists that his position has not changed.

You can see this pattern on display on a whole host of issues. For example, the deficit. Obama promised to cut the annual budget deficit in half by the end of his first time. Instead, he took a $1.186 trillion deficit, increased it to about $1.4 trillion, then finally dropped it down about 8 percent below the original tally. Yet as Philip Klein of the Washington Examiner has noted, even as the annual deficits repeatedly clocked in in at well above the trillion dollar mark, Obama continued to insist that his administration was on track to make good on his promise. "We are on the path to cutting our deficits in half," he said in 2010. "When I took office, I pledged to cut the deficit in half by the end of my first term," he said. "Our budget meets that pledge and puts us on a path to pay for what we spend by the middle of the decade." Needless to say, it wasn't.

Or look at how he's handled medical marijuana.

Running for office in 2008, he said he supports the "basic concept of using medical marijuana for the same purposes and with the same controls as other drugs." He was "not going to be using Justice Department resources to try to circumvent state laws." He told an Oregon newspaper that he would stop the Drug Enforcement Agency's raids on local pot clinics.

Yet as Jacob Sullum reported for Reason last year, that's not at all what happened. The pace of raids on medical marijuana clinics actually picked up under Obama, and at the time of Sullum's story were more frequent than under his Republican predecessor, George W. Bush. Obama now defends himself by downplaying his own authority to stop DEA raids and saying that "there haven't been prosecutions of users of marijuana for medical purposes."

As for those raids, well. Obama says it's a "murky area where you have large-scale, commercial operations that may supply medical marijuana users, but in some cases may also be supplying recreational users." And because of that, he says, "we put the Justice Department in a very difficult place if we're telling them, 'This is supposed to be against the law, but we want you to turn the other way.' That's not something we're going to do." The message? Anyone who was expecting raids to actually cease or slow down, rather than increase, was expecting too much. Obama didn't change his position. We just misunderstood it.

Obama's health care promises have been similarly full of twists and turns, even aside from his evolving support for the mandate he eventually signed into law. He promised, for example, that his plan would "cover every American and cut the cost of a typical family's premiums by $2,500 a year." But of course health insurance premiums have gone up since the passage of ObamaCare. Yet Obama insists that we're still on track. Over the last two years," he said at the first presidential debate, "health care premiums have gone up, it's true, but they've gone up slower than any time in the last 50 years. So we're already beginning to see progress." A somewhat slower rise is progress toward a cut?

As with his broken deficit pledge and his medical pot remarks, the President is insisting that we're moving in the direction he promised – despite clear evidence that in fact things are moving in precisely the opposite direction. And if things look worse at the moment, that can be explained away.

The reason flip-flops matter is because they suggest someone can't be trusted. But the same goes for Obama's excuses and evasions. Romney may be forgetting what his own positions are. But President Obama is ignoring or excusing his own actions.