As useless as these kinds of speculation are, it's even more worthless when Salon.com writes the headline:
If senators could rewrite history, the war wouldn't have happenedI don't know how many times we have to go through this. Even at the time, the White House was very clear: If they'd lost the vote in 2002, they were going to claim the right to invade Iraq based on the resolution passed after 9/11. The same way Bush claimed that if they lost at the UN, they'd still claim the right to invade based on the resolutions passed in 1996.
If the Senators had done their duty and voted against Bush, there would still have been a war. Bush would simply have ignored them. What their votes would have contributed was ending the war more quickly once it became the disaster it has.