Hillary voted "Yes" to give Bush the authority to use force to back up diplomatic pressure. Her specific words:
Today we are asked whether to give the President of the United States authority to use force in Iraq should diplomatic efforts fail to dismantle Saddam Hussein's chemical and biological weapons and his nuclear program.
snip
So it is with conviction that I support this resolution as being in the best interests of our nation. A vote for it is not a vote to rush to war; it is a vote that puts awesome responsibility in the hands of our President and we say to him - use these powers wisely and as a last resort. And it is a vote that says clearly to Saddam Hussein - this is your last chance - disarm or be disarmed.
http://clinton.senate.gov/speeches/iraq_101002.html-------
Compare to Wesley Clark's advice before the House Armed Services Committee in September of 2002, and you see a possible reason Hillary and other Dems voted as they did. From Wesley Clark:
"Our President has emphasized the urgency of eliminating these weapons and weapons programs. I strongly support his efforts to encourage the United Nations to act on this problem. And in taking this to the United Nations, the President's clear determination to act if the United Nations can't provides strong leverage undergirding further diplomatic efforts."
"The United States diplomacy in the United Nations will be further strengthened if the Congress can adopt a resolution expressing US determination to act if the United Nations will not. "
"The more nearly unanimous the resolution, the greater its impact in the diplomatic efforts underway."
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The lie that Hillary was pro-invasion, or that she voted to invade Iraq, or even that she supported Bush until recently on the matter, can easily be debunked with a little research.