The only way to pull that off without tipping your hand is by luring the equipment to the location under false or alternative pretenses. Election night will include multiple venues with the right equipment set up in large cities. The setup activities for Tuesday night are likely already in progress. That sure doesn't pin it down.
Also, OBL's last minute offer that we- the us people- are the only ones who can provide for our own security- that neither Kerry nor Bush can...suggests he wants a last minute message to appeal to world opinion....that, attacking us was his very last resort, we rejected the 8 appeals letter, etc....