Mitt Romney announced his run for the presidency today. It seems like he did this before, but that was the announcement of his exploratory committee. Such is the state of modern presidential politics that virtually nothing is unexpected. The Post reports:

Former Massachusetts governor Mitt Romney launched his second presidential campaign here on Thursday, officially joining a presidential field in which he is the nominal frontrunner.

In a speech declaring his candidacy, Romney delivered a broadside against President Obama, who he charged “has failed America.”

Romney said the federal government under Obama “has grown to consume almost 40 percent of our economy” and that “we are only inches away from ceasing to be a free economy.” He pledged that, if elected, he would “cap federal spending at 20 percent or less of the economy and finally, finally balance the budget.”

This was Romney at his best. He looks like a presidential candidate. He sounds like a grown-up. He has an articulate indictment of the president. But the trouble will start when he must interact with the media and his opponents.

As Joshua Green of the Atlantic put it, “He certainly was [convincing during the announcement] — he seemed comfortable, confident, and didn’t trip the way he often does over his scripted lines. Of the various political personas he has inhabited over the years — from liberal Massachusetts governor to social-conservative firebrand last cycle — the current one is truest to his actual background. You can see glimpses of a plausible Republican frontrunner.”

The problem is that there have been prior incarnations of Romney that the media and his opponents will bring up. If authenticity is the byword in grass-roots-driven politics then Romney will have to struggle to convince the voters that the current Romney is the “real one” and the one who will go to the Oval Office if elected.

Romney has both substantive and psychological hurdles to overcome with the voters. On substance, in comparison to 2008, the 2011 GOP is more libertarian, more devoted to the task of pruning government and reducing the size and scope of regulatory interference in the private sector. Romney’s greatest accomplishment is just such an interference, a health-care scheme that expanded the role of government. He is, to be blunt, very likely a cycle too late for the current GOP.

Second, Republicans are ever suspicious that they will be “robbed” and ”sold out.” Bush 41 wasn’t conservative enough. Bush 43 wanted an activist government. And don’t get them started on Justice David Souter. Romney exacerbates these fears. Heck, he already “sold out” with RomneyCare. He may promise the sun and the moon, but the base frets that he does not have the mettle to withstand the onslaught of criticism and opposition that a president must endure.

This isn’t to say Romney’s cause is hopeless. The appearance of Sarah Palin, literally and physically, on the fringe of his campaign (she road into New Hampshire as Romney was finishing his speech) enhances his credibility, serving as a reminder that Republicans can’t merely run against Obama; they must have a credible alternative. Right now, Romney is one of the few contenders who is.