John McCain, speaking for the Senate Republicans, on why the Webb amendment is a bad idea:

The Constitution of the United States gives no authority for the Congress of the United States to set lengths of tour or lengths of duty in the military.

A fine point, albeit confusingly said, except for the fact that it's plainly not true (Art. I, sec. 8: "The Congress shall have power... to make rules for the government and regulation of the land and naval forces."). In other words, as Harry Reid shot back,

Anyone that suggests that the Webb amendment is unconstitutional either is not reading the law or no one's explained it to them very well.

Indeed.

(Amusingly, the other major argument against the Webb amendment [an argument that made its way around the Sunday talk shows this weekend] is that it would force the military to tackle "a management nightmare: having to track the service in Iraq of each soldier." Because Lord knows we wouldn't want that.)