Mystery:Why Did Santorum Quit?

See Endorsements 2012 for how Conservapedia predicted long ago that Rick Santorum would endorse Mitt Romney.

Rick Santorum abruptly terminated of his campaign for the Presidential Election 2012 on April 10, leaving many conservatives stranded. Unlike Rick Perry, who immediately endorsed pro-life candidate Newt Gingrich upon quitting, Santorum said he would help RINO Mitt Romney. Why did Santorum surprisingly quit so suddenly?

Possible explanations include:

• as a stalking horse for Mitt Romney, designed to block other conservative challengers, Santorum had accomplished his goal
• Santorum wants to endorse Romney, as he did in 2008, and needed to pull out now to facilitate that
• As noted long ago by Conservapedia, Santorum would exit the race once he began pulling more votes away from Romney than from other conservative challengers, which probably did not occur until early April
• the economics of Santorum's campaign had worsened (but this hasn't caused Newt Gingrich to pull out)
• Mitt Romney's campaign was about to spend millions in Pennsylvania, and Santorum had to pull out now or else lose any future opportunities with Romney
• the Establishment pressure on Santorum became too great for him to withstand
• several establishment-type pro-life groups planned to endorse Romney the same week, and Santorum did not want to disagree with them
• Santorum could not win his home state of Pennsylvania on April 24, and that loss would have undone the credibility that Santorum had gained
• Santorum has often campaigned for RINOs against conservatives, as he did for Arlen Specter against Pat Toomey, and now Santorum can campaign for Romney against Gingrich
• He had less than half as many delegates as Romney and knew that victory was out of his grasp.
• Santorum says it's because his campaign was broke.
• The decision by Texas not to award the primary winner all delegates was a major setback to his chances.
• His child needing constant medical care may have been a reminder that he couldn't devote his all to the job.

(add to list)

A similar question is this: how soon will Santorum begin campaigning against pro-life Newt Gingrich?