Might have hesitated to make this remark if I'd anticipated so much curiosity and skepticism about it, not because I think it's wrong, but simply because I'm not too invested in litigating counterfactuals about a war that began more than a decade ago. Still, perhaps it's worth remembering that from the very invasion of Iraq, the American left saw the war as a bipartisan effort that could never be pinned entirely on George W. Bush. Some key points:
1. The Iraq Liberation Act, which made it "the policy of the United States to support efforts to remove the regime headed by Saddam Hussein from power in Iraq," was passed in 1998 under Clinton/Gore.
2. On that basis, Clinton/Gore actively provided political and even military support to anti-Hussein opposition groups in Iraq. Among other things, this included CIA support for bombing and sabotage campaigns by Wifaq, a militant group trying to mount a coup against Hussein.
3. Also on that basis, Clinton/Gore actually launched a military intervention in Iraq, Operation Desert Fox. Despite significant domestic and international opposition, absent Congressional approval, and absent direct UN authorization.
4. 9/11 created two enormous political incentives that would have created pressure for any administration to go to war. First, the intelligence and defensive failures precipitating 9/11 were enormous political liabilities that demanded a dramatic and proactive response. This is particularly true given the public's dissatisfaction with progress in Afghanistan. Second, 9/11 was always going to provoke an unfocused drive for retaliation among reactionaries, and demand a show of strength among Americans with ideological / psychological / financial investments in American empire. Clinton/Gore never faced drives to war of this magnitude, and yet even absent such incentives they still engaged in multiple military actions.
5. 9/11 also removed enormous political deterrents that kept Clinton/Gore from expanding their ambitions in Iraq. First, it damaged the reputation and influence of foreign policy elites who argued for a constrained role for the American military. Second, it undercut international diplomatic and economic opposition to American interventions. Third, it undercut domestic resistance.
In short, Gore supported past interventions in Iraq, accepted two major arguments for further intervention (pre-emptive defense and humanitarian), would have been subject to tremendous pressure to go to war, and would have been freed from many of the major disincentives. Moreover, in his own direct statements on the matter at the time, Gore's major objection to war was a preference for more international support - a preference that he had a record of setting aside in the past.
There's a more detailed argument to be made here, but that's a start.