As Buzzfeed notes, Mitt Romney (R-Am I the Nominee Yet?) is running radio spots (via Talking Points Memo) in Illinois that say this:

Is Rick Santorum electable? Remember his last Senate race? … By historic margins, Pennsylvania voters rejected Rick Santorum.

But, as Buzzfeed points out, Massachusetts voters rejected Mitt Romney by virtually identical margins.

Worse, “Romney . . . lost big in a historically good year for Republicans, while Santorum lost big in a historically bad year for Republicans.”

Helpful Buzzfeed chart:

Not to get technical about it.