So it was noteworthy last week that when Romney addressed supporters after his New Hampshire win, he got serious and gave an actual speech, which he read from a teleprompter - a device he once mocked Obama for using.
It was a good speech, as campaign speeches go ...
His case? That he is a rock-solid conservative, not the closet moderate that some voters dread and others hope for.
In his speech, Romney made it clear that he now considers himself running against Obama rather than the rest of the Republican field. He excoriated Obama for the disappointments of the last three years, calling him "a failed president."
But then Romney went further.
"This president takes his inspiration from the capitals of Europe; we look to the cities and small towns of America."
Talk about playing to the Tea Party. Romney's theme - and it was far more extended than I'm reproducing here - was a barely veiled evocation of the old charge that the president isn't a real American.
But it raises a question. Is Obama modeling his policies on European principles? Hardly. His fiscal approach of continued stimulus is actually the opposite of Europe's prevailing austerity policy. On Obama's central policy effort, universal healthcare, he looked not toward Europe but to Romney's own state of Massachusetts.
More to the point, though, most voters outside the Republican Party base don't really think Obama is a closet European - or a gloomy pessimist, for that matter. The patriotism gap Romney is trying to create is a device to mobilize Tea Party votes, not an appeal to the center. But as Republican red meat goes, it wasn't bad.
And there was more. "President Obama wants to put free enterprise on trial," Romney said. "In the last few days, we have seen some desperate Republicans join forces with him."
In case that wasn't clear, Romney escalated the argument in an interview on NBC on Wednesday, charging that the debate about income inequality is divisive and unpatriotic.
And here Romney, under pressure of the bitter politics of his primary campaign, has given Obama an opening to exploit. Most Americans are, in fact, worried about the declining incomes of the middle class, and a solid majority favor raising taxes on "millionaires and billionaires," to use Obama's deliberately divisive phrase. If Romney wages a campaign that focuses on defending the top 1 percent against the worries of the rest, he's leading with his chin.
Romney did stand up for the middle class last fall, when he defended his relatively moderate proposal to abolish capital gains taxes for households earning less than $200,000 a year (instead of for all households, as most of his rivals for the nomination prefer). But now his rivals' attacks on his record as a venture capitalist appear to have pushed him further to the right.
Romney was once a Republican version of a centrist; he's refashioned himself, doggedly, into a real conservative. But all the vitriolic rhetoric raises a big question: Will any voters in the center be able to convince themselves that he's still a closet moderate? Romney, and the GOP, have to hope so, but their own campaign is making the task harder, not easier.
Doyle McManus is a columnist for The Los Angeles Times. Readers may send him email at doyle.mcmanuslatimes.com.