If we're going to discuss Santorum's last campaign, let's include the result.
From Wiki:
In the November 7, 2006 election, Santorum lost by over 700,000 votes, receiving 41.3 percent of the vote to Casey's 58.7 percent, the largest margin of defeat ever for an incumbent Republican Senator in Pennsylvania.[36] The 18-point defeat was the largest margin of defeat for any incumbent senator since 1980[37] and the largest margin of any incumbent Republican senator ever.
Which means Santorum has secured the votes of about 15 times as many people as Gingrich ever has.
Meanwhile, if we are looking at which candidate last won an election, that would be Santorum. Gingrich’s last election was in 1998, Santorum won in 2000.
Would Gingrich have won if he had run for that Senate seat in 2004 that Cain ran for? Do you think he wouldn’t have run if he thought he could win?