Time to go back in the past, but not very far.
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Most politicians drop out of races when a mistress comes forth, nearly all of them do so when a pregnancy scare arises from their misdeeds. But only a few are classy enough to do so when their actual spouse becomes pregnant. Such was the case for Mitt Romney, who dropped his bid for President late 2011 right after the announcement of their 6th kid citing his refusal to divide his parental responsibilities with those of his Presidential ones.
This gave the other Republicans a few weeks to readjust their strategies, and with Ron Pauls fairly big victory in New Hampshire he became the frontrunner. Except he didn't. Despite taking over 40% of the vote, to Huntsman's 26% and Santorum's 22, he received little attention from the mainstream media. Santorum's 1st place finish in Iowa (after Paul and Romney, who was still on the ballot, embarrassing the contestants who were actually running) and his decent showing in NH gave him the early lead . The Southern caucus's slowly gave Santorum build-up after build up (even after an incident in South Carolina where he claimed a "few too many black Democrats were voting against him") to launch a Super Tuesday finale. Western states were a little kinder to Paul and Huntsman, but most had dropped out by Super Tuesday and backed Santorum.
Despite the rather overwhelming victory Santorum received, some were off put by his open and loud opposition to issues many felt distracting from a professional campaign. While most were on abortion, homosexuals, and the usual, he seemed to battle more with members of his own party then President Obama. At a campaign stop in Arizona he called McCain the "surrender candidate" that let Obama win. Some speculate this to be an attack in retaliation for McCain calling him a "man who makes Goldwater look [like a] New Dealer", and that Obama "at least had his head under the clouds." His attack on Libertarianism and it's "Ayn Randian hatred of God [that made him] shudder" encouraged Ron Paul, already upset how he was treated by the media and the Santorum campaign, to support Johnson for President. Somewhat ironically, or maybe fittingly, he ran slightly to the left of the Obama campaign on some economic issues, calling for further increases of education, autism research, and child care for poor families.
The biggest injury to the Santorum campaign wasn't the message, it was Santorum's attempt to market it. He insulted everyone, backed the most unpopular members of his party (most infamously when he declared Indiana Senate candidates rape comments as "common sense to people who know anything on human biology." He lead the election cycle after his nomination, but his treatment of his own party lead to alienation from them, his stiff debate performances made him look strangely unenthusiastic compared to his normal bombastic persona, and his repeated embarrassments made the Obama re-election more then Obama made the Obama re-election.
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First of the Runners-Up Retrospective, counting backwards from 2012 to somewhere in the early days of American politics, we have the Obama-Santorum smackdown. I imagine Santorum, with the camera's perpetually on him would dig his own grave and make Obama's job much easier. His ties to Mourdock damned any chances of taking Indiana by normal margins, encouraged Southern blacks and Independents to turn in large numbers against him (and make white conservatives a bit more enthusiastic). Arizona I don't think would take all well to the man, his anti-Mormon comments would drive those numbers down (600,000 of them in a state decided by less then 200,000 votes), McCain might be bitter enough to support Obama (if by omission), Libertarians would probably push Johnson to 2 or 3%.
Thoughts so far?