In 1968, Richard Nixon campaigned on the apparently vapid slogan: "Nixon's the One." In truth, it was both clever and accurate, revealing the nature of Nixon's appeal — the reductionist reason he ultimately won both the GOP nomination and the White House.

Nixon almost fell short in November after his Democratic rival, the incumbent Vice President Hubert Humphrey, finally, gently — perhaps too gently — broke with Lyndon Johnson and called for a halt to the bombing of North Vietnam. In the end, though, the recycled Republican who had lost to JFK in 1960, and who had a secret plan for peace, seemed to a narrow plurality of Americans the safer bet to wind down the war and crack down on racial violence and rising crime at home.

The third-party candidate in 1968, the segregationist governor of Alabama George Wallace, took votes from Nixon, but not enough to deny him the presidency. Nixon had taken up enough of Wallace's grievances — for example, school busing — and code word–coated them so he could plausibly disclaim an appeal to prejudice. It was Nixon's "southern strategy." And here, too, he became the only practical, electable choice for those that wanted their votes to count and counter the civil-rights revolution.

Romney may never command Republican emotions; like Nixon, he's a candidate of head, not heart — of calculation, not deep conviction.

Still, it was in the primaries where Nixon's slogan so presciently told the tale of the tape. When the candidates were weighed in the balance, he was the only one — not charismatic, but acceptable; the choice not of enthusiasm, but of realism. The one who won because his opponents lost. They were a formidable crew — far more serious figures than the near caricatures in the 2012 GOP field, but each flawed in a different and fatal way.

New York Gov. Nelson Rockefeller dithered before entering and alienated some of his pivotal supporters, like Maryland Gov. Spiro Agnew, who as Nixon's soon-to-be running mate ranks high in the pre-Palin list of far-fetched VP choices. Rockefeller was too moderate anyway — in the eyes of too many in the GOP, guilty beyond a reasonable doubt of the mortal sin of liberal Republicanism.

On the other hand, Ronald Reagan, with the last-minute launch of the first of his four runs for the White House, was too far right in the prevailing unwisdom of the GOP establishment: He could never make it in a general election.

And George Romney, the popular governor of Michigan, and a fresher face than Nixon, spoke his own doom when he said that on a trip to Vietnam he had been "brainwashed" by U.S. generals and diplomats. Americans don't choose a self-confessed Manchurian candidate as their president.

Ironically, it's Romney's son who's steadily, and now increasingly, emerging as the Nixon of 2012 — and not just in his contrived eagerness to conceal his real persona, whatever it is, and pander to the fears and anger of voters. Thus Romney has his plan for jobs; it's not a secret one like Nixon's plan to end the war, but it's equally fraudulent, a list of right-wing nostrums recast in the image of his famous — and fictional — record of job creation in the private sector.

Like Nixon, Romney has something more important — the gift of opponents who are proving his case for the nomination. Put aside the patent absurdity of Michele Bachmann, Herman Cain, Newt Gingrich — and the quixotic quest of Jon Huntsman, a Rockefeller relic in an adamantly right-wing party where there are no Rockefeller Republicans left. Instead think of Rick Perry, whose spectacular rise and abrupt and accelerating fall are pushing pundits, party insiders, and primary voters toward the conclusion that Romney is all Republicans have, and just good enough to settle for, if they're actually focused on beating Barack Obama.

The conventional response here is that it's too early, that any such rush to judgement is ahistorical. And it's easy to cite misplaced analogies that miss the point that the political calendar doesn't march in lock step every four years.

Some point to the 2004 Democratic contest. John Kerry was far behind, falling fast in the autumn before the Iowa caucus. But at that moment, Democrats were rallying to Howard Dean out of an emotional reaction against the Iraq War. As they turned to another critical question — "Who's a plausible president, who has a chance to beat Bush?" — Dean's support drained away. Indeed, like Perry at the other end of the spectrum, Dean was prone to reckless statements like the one in which he said that he wouldn't assume Osama Bin Laden was guilty for 9/11. That came just weeks before caucus day — but combined with his hot presence on the stump, it was as lethal as Perry calling Social Security "a Ponzi scheme" — and then telling Republicans they're "heartless" for opposing in-state college tuition for the children of illegal immigrants.

We've also been reminded that at this time in the 2008 cycle, Rudolph Giuliani and former Sen. Fred Thompson, who had previously retired to a supporting role on Law and Order, were leading the GOP horse race with an underfunded John McCain lapped and all but written off. This ignores the fact that McCain had an underlying strength: He wasn't the favorite of movement Republicans, but he was heir to the unwritten Republican rule of nomination by primogeniture. It was his turn — and he turned out to be the once and future frontrunner as Thompson fizzled in debates and primary voters discovered Giuliani's pro-choice position and his semi-tolerant attitude toward gays.

Although he's never experienced McCain's campaign money woes, Romney has already had his own fall from grace this year, an abrupt drop in the polls when Perry materialized out of the conservative West. The difference is that Romney is recovering faster than McCain did; the similarity is that Perry has a case of Thompson's debate impairment — only worse — and the Texas governor's immigration comment has offended the base even more swiftly than Giuliani did on social issues. Perry's now backed off his "heartless" comment but the imprint will remain — and overall, the impression that he's inept was so instant, so powerful, that it may be indelible.

Finally, there's the suggestion from the smart, sometimes cynically smart, Mark Halperin of TIME and Game Change fame that "Santorum...could soar in Iowa... [and] Huntsman is showing life in New Hampshire" — which could be a threat to Romney. This is a woulda, coulda, shoulda thing that could happen in an ultimately unknowable future; but from what we do know, it's unlikely. The beneficiaries of Perry's fade in Iowa, according to the latest ARG survey, are Romney, who's now in first place there, and Bachmann, who's second. If Romney plays and prevails — or comes close — in the ultra-conservative GOP electorate in Iowa, the contest nationally could be over early, with the Iowa results confirming and solidifying his ingrained strength in the Granite State, sustaining him through South Carolina, and propelling him in Florida, where Perry's unrepentant Social Security–bashing has suddenly handed a six-point lead to Romney.

The trend across the board is Perry moving down and Romney moving up. As I've argued, Democrats would prefer to run against the Texan; but given his prospects in swing states like Florida and Pennsylvania, his nomination would manifest the GOP as the party that has genuinely lost its head. Romney may never command Republican emotions; again, like Nixon, he's a candidate of head, not heart — of calculation, not deep conviction. So gravitation toward him may be grudging; he may inch up rather than soar. But in the absence of someone more resonant with the base who also looks like a possible winner, Republicans will almost certainly wish and rationalize away their doubts about Romney's shape-shifting ideology.

Even the last-gasp search for an alternative — how about the tub-thumping governor of New Jersey Chris Christie? — points to the gathering realpolitik of this race. If Christie doesn't run — and if he did, he might in his own inimitable way relive Perry's wild ride — where can the party go other than to Romney?

There's a final parallel to Nixon here. His November 1968 victory was probably saved when his operatives covertly persuaded the South Vietnamese government to boycott and sabotage the Paris peace talks. This time, congressional Republicans — whether they're for Romney or not — are attempting to smooth his path, or any Republican nominee's, to victory in November. Their obstructionism on a jobs bill and their insistence on austerity may be a matter of ideology, although that didn't bother them when George W. Bush was the biggest deficit-driver in history. But it's also impossible not to believe that Republicans see a jobless recovery as a way to recover the job of president. The party of "morning in America" has become the party of twilight in America — and aims to profit from it.

This could backfire and House Republicans know it — which is why they haven't done something as obvious and odious as shutting down the government, even while they're busy shutting off economic growth. And while Romney may be the most viable — the only viable — Republican, he's also vulnerable, not just for his flip-flops, but for his record. Can a jobs destroyer as a venture capitalist, or a jobs laggard as a governor — Massachusetts ranked 47th in job creation when Romney was in office — convince the country that he will be the jobs president, or to take a chance that he might be better on the issue than Obama?

That's the post-convention question. Right now, Romney is gradually convincing the GOP to live with him — or at least that there is not enough life in anyone else. Clearly, his progress is not a matter of Reaganesque affirmation. NBC's First Read observes that stories in both The Washington Post and The New York Times are asking: "Why hasn't Romney caught fire?" He can't — and doesn't have to. Romney's victory will be found in the embers of rival candidacies.

Sure, other scenarios could play out. But more and more, the odds are that Romney's the one.