Perhaps there's some validity to this complaint, but I think a lot more of it stems from confusing what you say about your opponent with what your opponent is actually like. It's a given of recent electoral politics that the Republican is a virtual libertarian who wants to give the rich tax cuts while taking money from the poor, and also that he's a raving warmonger eager to pursue wars of choice. The script runs regardless of who becomes the candidate. In 2008, when long time media and "moderate" darling John McCain was nominated by the GOP, he suddenly became a defender of the rich and a raving war monger instead of, well... John McCain. Now we have Mitt Romney, a Republican sufficiently squishy that it took him a long term to lock up the nomination (since everyone in the GOP base kept hoping that a more conservative option would show up) and whom several of my conservative friends have announced they will vote third party rather than support in order to teach the GOP a lesson. But, the script runs anyway, and so people are now shocked when he showed up at the debate and didn't suggest turning the poor into processed meat to grace the tables of the rich.
Clive Cook of The Atlantic feels that Romney may have played everyone for a dope:
I'd say this puts conservatives cheering Romney's big debate win squarely among the dopes. They've been played by their own candidate, according to this narrative. Maybe they haven't realized, or maybe they have and just don't care, so long as Obama goes down to defeat.
It also helps that Obama would be the biggest dope. His entire campaign, with Romney's unstinting help until this week, has arranged itself around Romney the evil capitalist, Romney the scourge of entitlements, Romney let's-make-the-rich-richer. When Romney the pragmatic moderate turns up instead, it's not very powerful (even though it's true) to reply, "But that's not what you've been saying up to now." A bit juvenile, somehow, to say, "Can't take it back. Can't take it back," which was Obama's first post-debate line of defense. Less than effective to counterpunch with, "We're just going to keep on attacking the man we thought you were, otherwise it's not fair." Also, the severe Romney has encouraged Obama to speak mainly to his own base, calculating that GOP extremism would deliver centrist votes to the president. The Obama campaign hasn't locked in the center's support, as it otherwise might have.
The thing is, while Romney has been singularly hapless at times, he hasn't been campaigning as "Romney the evil capitalist, Romney the scourge of entitlements, Romney let's-make-the-rich-richer", that's just what the Obama campaign has been saying he's campaigning as. It would be one thing if Romney had actually been insisting that he wanted to raise taxes on middle class families by $2000/yr while giving huge tax cuts to the rich (as Obama ads on Pandora have been telling me every ten freaking minutes for the last few months) and then he showed up to the debate and insisted to everyone's surprise that he wouldn't raise taxes on the middle class. That would be a real tack to the center. But in the real world, the Romney campaign has been insisting all along that they wouldn't raise taxes on the middle class. It's just that they conspicuously failed to get that message across very clearly until Romney and Obama found themselves facing each other on a debating stage and it suddenly turned out that the candidate Obama has been attacking all this time doesn't exist.
In a year when both candidates are pretty bad (though, obviously, I find Obama the worse of the two), this says a lot about the failures of both campaigns. Romney completely failed to get an accurate version of his message out to the electorate for most of the election reason, allowing himself to be characterized by his opponent. At the same time, the Obama campaign was so focused on negatively characterizing their opponent that they seem not to have noticed that some time ago the thing they were attacking ceased to be the real world Romney campaign. Without the debates as reality check, this might have worked fine right up till election day. It may still work. Romney is not the strongest candidate and Obama has the traditional incumbent's advantages. But much of Obama's implosion on the debate stage (and Romney's subsequent surge in the polls to a virtual tie) seems to have been the result of the Obama campaign starting to believe their own line and live in their own bubble.