2012: Rick Santorum the Republican nominee

[Blow by blow, the passion dies]

I can see him losing badly

[Agonized-Statism]

President Barack Obama (D-IL) / Vice President Joe Biden (D-DE) ✓
Fmr. Senator Rick Santorum (R-PA) / Congresswoman Michele Bachmann (R-MN)

[Blow by blow, the passion dies]

Too socially conservative and controversial

[Fuzzy Bear]

He'd have lost, but he was more economically liberal than Mitt Romney.  Santorum at least voiced concern for working people and not just the "job creators".

[NewYorkExpress]

Santorum's popularity among evangelicals flips Iowa, North Carolina and Indiana from 2008.

Conversely, his unpopularity among Independents allows Obama to win a wider popular vote margin, though Santorum's strength among evangelicals keeps Obama from winning any other states that he didn't win in 2008, and Pence being on the ticket gives Santorum a wider than expected win in Indiana.

POTUS Barack Obama (D-IL)/VPOTUS Joe Biden (D-DE) 54%
Former Senator Rick Santorum (R-PA)/Representative Mike Pence (R-IN) 45%

[DPKdebator]

Santorum's popularity among evangelicals flips Iowa, North Carolina and Indiana from 2008.

Conversely, his unpopularity among Independents allows Obama to win a wider popular vote margin, though Santorum's strength among evangelicals keeps Obama from winning any other states that he didn't win in 2008, and Pence being on the ticket gives Santorum a wider than expected win in Indiana.

POTUS Barack Obama (D-IL)/VPOTUS Joe Biden (D-DE) 54%
Former Senator Rick Santorum (D-PA)/Representative Mike Pence (R-IN) 45%

Obama was pretty popular in Iowa, so I doubt Santorum flips it.

[BushKerry04]

[TocoToco]

I think Santorum most likely picks a Running mate that isn't as socially conservative as him for starters.Also one that is viable to an advantage in the Electoral Map.For this instance he goes for Rubio.However this and many more choices that he makes in the campaign trail that are smarter than Romney's,this doesn't give a Victory on Election Night,doing worse than his Republican counter-part with 191-343.

Santorum loses North Carolina by about 4000-7000 votes,closer than Romney's win and Iowa is closer as well.I don't think he does awful in Arizona and Georgia as others think due to energizing the Evangelical and Social Conservative Vote more than Romney did.This does set him back in Ohio,Wisconsin and New Hampshire though,as these swing slightly towards Obama.
As for Pennsylvania,he does worse than Romney,Despite getting more working class support than Romney does,the general consensus towards Santorum in Pennsylvania is not favourable by the bit,a little less if he wins their Primary.
Anyways,give or take North Carolina and Iowa i suppose on this.