portkey conundrum

[naama_gat at hotmail.com]

No: HPFGUIDX 6231

There is a point that is very puzzling to me in the Goblet of Fire
plot, and its to do with 
the trophy cup being made into a portkey by the fake Mad Eye Moody: 
Harry being manipulated into the contest, being secretly helped by
Moody - all this is to 
make Harry the winner of the triwizard contest, thereby making him
the first to touch the 
trophy cup, thereby whisking him away to Voldemort. My question is
this - why couldn't 
Moody turn any object into a portkey and then give it to Harry to
touch? why was the whole 
long and involved process of the contest necessary? Is there a point
in the story that I've 
missed?

Naama