Where does it come from? I think Ben's hunch that it could be an idiom blend seems spot-on. Two idioms we are comfortable with, "razor-thin margin" and "tight race," are conjoined here to make a razor-tight race.
Ben—who knows a thing or two about tracing things back to their origins—has found "razor-tight" in use as far back as 1955, and he may not be finished with it yet.
I nevertheless nominate "razor-tight" for the Common Errors in English Usage site, at least on the "More Errors" page, where we find a listing for "focus like a razor" (instead of "focus like a laser"). There is a natural urge to associate razors with things that are very close or concentrated, and while I admire those who push the boundaries, I am going to stick with razor metaphors that convey actual properties of actual razors. I agree with the commenter Wood F.:
Properties of razors are that they are "thin" and "sharp." So razor-thin and razor-sharp make sense. Razors can provide a "close" shave, so "razor-close" makes sense (even though razors themselves are not "close"). But what about razors is "tight"?I think Stephen Colbert agrees, too:
|The Colbert Report||Mon - Thurs 11:30pm / 10:30c|
|"Razor Tight" Presidential Election|