Perplexing but true: Mitt Romney is on the glide path to the most easily secured nomination a Republican presidential candidate has ever had — while being one of the weakest major candidates either party has ever seen.

It is entirely possible that Romney will win every major contest from here on in, just as he won New Hampshire last night and Iowa last week. He is already leading in the South Carolina polls (that primary is on Jan. 21) and has a huge margin in Florida (Jan. 31).

Perhaps if Rick Santorum, who basically tied with Romney in Iowa, had translated his success there into New Hampshire momentum, a race would’ve developed. But Santorum didn’t come within 25 points of Romney.

And while Romney is bracing for a colossal onslaught of negative ads in South Carolina — both Newt Gingrich and Rick Perry will be spending millions on TV there to tear him down — what exactly is the alternative to Romney now?

Perry? It’s unimaginable that the candidate who embarrassed himself in debate after debate, month after month in 2011, can suddenly find his voice and his sea legs and his authority.

Gingrich? His harsh line of attack against Romney’s career at a private investment firm has clearly backfired with the Republican base, as exemplified yesterday by the extraordinarily heated denunciation of Gingrich by Rush Limbaugh — who is, to put it mildly, not a Romney fan.

Limbaugh likened Gingrich to Occupy Wall Street and The New York Times — and his comparison, which could not strike a conservative’s ear any more negatively, is going to stick in a place like South Carolina.

The second-place finisher in New Hampshire was Ron Paul — who benefited from the fact that there are plenty of college kids in New Hampshire willing to take advantage of the state’s open primary to cast a ballot for an isolationist who wants to legalize marijuana.

Paul will certainly stay in it with Romney all the way. Somebody has to. And that is not good news for the Republican Party, which will have to reckon with possibly ill-behaved Paul delegates at the convention in Tampa in August — delegates who might heckle Romney from the floor and otherwise disrupt his coronation.

But Republicans will vote for Romney in the primaries. Voters tend to take their responsibility seriously, and they want to vote for someone who is a serious candidate. And because every other plausible major candidate refused to run in 2011, Romney has been the only serious candidate in the race.

But nobody loves him. No one is inspired by him. He cuts an impressive figure and is clearly very intelligent, but he is a man without an ideological core.

Claiming he should be president because he knows how to run a business may be the least stirring message any candidate has seized upon since Michael Dukakis foundered in 1988 by claiming he could bring “competence” to the White House.

And his liabilities are undeniable. Even though Gingrich’s assault on Romney’s record of laying off workers when he was running Bain Capital is breathtaking in its disingenuousness, that record does happen to be one of a dozen glaring weaknesses in Romney’s biography, political history and approach that President Obama and his team will be able to use to their advantage.

So he will win the nomination in a walk. But he will be beaten and battered by the time he crosses the finish line in November — though he may well do so in first place.

Because, while his own record is problematic, Barack Obama’s is worse.