Mitt Romney ended the New Hampshire primary with a decisive—albeit expected—victory and has a strong chance to win the January 21 primary in South Carolina as well. His purportedly strongest opponents in South Carolina—Newt Gingrich, Rick Santorum, Rick Perry—have little or no momentum and are unlikely to cause an upset at this stage. After just one week of primaries, only one first-tier candidate remains and that is Romney.

Last night, Mitt Romney spoke like he was already the nominee. He spoke early, was on message and delivered a blistering attack against President Obama. The highly scripted candidate knows it’s over for the nomination, and he wanted to convey the aura of a prospective president.

Mark this one as a victory for establishment Republicans over the Republican base. It shows that the GOP remains an electoral force and that it will ultimately choose a candidate that can appeal beyond the party’s base when it comes to a presidential contest. That lesson was learned back in 1964, when the GOP went outside the mainstream to pick Barry Goldwater and lost in a landslide.

Sure, the party has very vocal factions and can sometimes appear very divided. As we have seen in this campaign, Newt Gingrich has an unrivaled capacity for confrontational politics, while Ron Paul has a similar affinity for fringe politics politics. But while a different candidate kept emerging to challenge the inevitability of Romney’s nomination, the former Massachusetts governor kept accumulating endorsements, strengthening his organization, and raking in money.

Romney’s opponents, by contrast, have been unable to sustain any surge. The first two contests in Iowa and New Hampshire have uncovered no meaningful threat to Romney. As long as Santorum and Gingrich both stay in the race, any serious anti-Romney movement will be too divided to succeed. Ron Paul would be a greater threat to Romney as a third-party candidate than as a rival for the GOP nomination. Jon Huntsman, despite his bravado-filled speech in New Hampshire, was never a serious candidate because of his work with the Obama administration. And Rick Perry’s campaign is entering its final days.

Romney’s campaign should nonetheless keep in mind it is still a long way to November. Cracks began to emerge in the latter days of the campaign about his work in the private sector. Gingrich will be hitting him hard about it in the days ahead in S.C., and Obama will not get any less aggressive down the road. Expect this to go on and count on a closer scrutiny of his record as governor.