From a historical angle, here are Rand Paul's:
The last three senators the GOP nominated for president, McCain, former Sen. Bob Dole (R-Kan.) and former Sen. Barry Goldwater (R-Ariz.), all lost by more than 190 electoral votes and by an average of 282 electoral votes.
The truer average is interesting, in that it suggests how little has changed since the South went Republican, or, if you prefer, since Republicanism went south, in '64. Sen. Goldwater may be an outlier--he lost to President Johnson by a skewing 434 electoral votes--but ultimately he became the GOP's enduring foundation of presidential troubles.
Sen. Dole lost to Bill Clinton by 220 electoral votes; Sen. McCain to Barack Obama by 192. Their average loss: 206. Take that average--computed as the differential between winning and losing candidates--and use it in a slightly different way: simply subtract it from 538. The result, 332. Now forget all that and just go to an interactive map, then give Hillary Clinton all the reliably Democratic electoral votes and give Rand Paul all the reliably Republican electoral votes. What do you get? A finish of 332-206.
Of course the really astonishing part isn't that Goldwater's reactionary turn has ultimately trapped the GOP in a long-term hole of diminishing returns, which it has. It is, rather, that even a Rand Paul could pull in about 150 more electoral votes in 2016 than Goldwater could in the still lily-white atmosphere of 1964.