Tough-movement and raising

[pne]

The grammar of the Niuean language that I have (by Seiter, IIRC), uses the term "tough-movement" (I don't remember off-hand whether he used the hyphen in the book or not).

I recently came across this term again on the CONLANG mailing list, and don't really know what it means.

Apparently, it involves or is related to raising, which I think I sort of understand from the examples given, but I don't know what to make of tough-movement.

Can any of the linguistics geeks on my friends list provide any insight on TM and possibly raising? isabeau? pthalogreen?