I'll grant DHS probably doesn't get created because the line of attack on 9/11 out of the gate would be that we had too much beauracracy preventing the CIA and FBI from doing their jobs and creating a new layer would not help; and the Delay/Hasstert House would not create a new cabinet department for Gore;
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Tax cuts are probable since both parties were into them, at that moment
Iraq is possible; Gore himself and many of his key allies were interested in going into Iraq since at least 1996; although the republican house may put breaks on it
Again, you're basing your assumptions on the attitudes that prevaled in the years prior to 9/11, once the towers fall all bets are off. Tax cuts were popular with a congress that didn't have to worry about paying for a massively expensive war in Afghanistan and we had a massive budget surplus. Also, Gore wanted to go into Iraq without the massive military obligation involved in going to war in Afghanistan. The political landscape was very different prior to 9/11, basing your assumptions on what politicians supported beforehand is faulty to say the least.
The big thing is that Gore has a very good chance of being crippled by 9/11; the people in charge of the National Security structure have been there a long time and there was 93 towers and the Cole without doing anything in response; Bush was only able to shake the immediate charges of incompetence by saying that he just got there and none of his people were confirmed by the Senate. Gore has no excuse and never was the most gifted speaker in the party; and with an opposition congress, there will be immediate commissions into administration failures which will show him involved in the committee that created the wall of seperation
And despite the absolute hatred that the GOP has always had for Bill Clinton, he has never suffered too much in the court of public opinion for his role in the bureaucratic atmosphere which allowed Al Queda to pull off 9/11. Bush managed to get carte blanche to pass the Patriot Act, conduct torture, and launch a war based on bogus evidence as a result of the political capital he got following the attack. It lasted him the entire rest of his first term and more or less bought him a second, despite failing to find OBL, and despite fighting an increasingly unpopular war. Really, I don't see the GOP or Gore's opponent(presumably McCain) dabbling in such dirty tactics in the aftermath of the failure of Karl Rove's own tactics in 2000 and similar moves by the GOP throughout the 90's against Clinton.
The republicans may not be bold enough to try impeachment again after their failure to ouster Clinton just 3 years before but they may inflict a catestrophic drubbing in the 02 midterms (maybe even getting close to overriding veto power) and Gore may decline to run in 04
Can I have some of what you are smoking?