With regards to Clinton's numbers in New York in 2000, you have to remember that she was at a disadvantage not being a native of the state. Lazio essentially had the home state advantage like Bush in Texas in the Presidential race.
Her 2006 numbers will be more indicative of her overall vote getting ability. Whether or not she pulls a higher percentage of the vote than Kerry or Gore got in New York will be meaningful.
It would be meaningful against a credible opponent, but it appears that Hillary won't have a credible opponent.
The best shot was Jeanine Pirro, and she made a fool of herself. The state's Republican party has imploded, and can't even field a candidate for governor, much less senator.
Under these circumstances, I'm not sure how meaningful Hillary's percentage will be as an indicator of how she can perform nationally.
In 2000, she ran below Gore in New York by about 4 points, and that could be telling. Since Gore essentially tied the race nationally, that can only mean that Hillary would definitely have lost.
I wish she had a credible opponent in 2006 because I agree with your theory and would love to see it tested, but I think the circumstances of this particular race undermine the operation of your theory.
Clinton's 2000 numbers were down because she was seen as an out of stater, that isn't the case anymore she is seen as a New Yorker. This really hurt her on Long Island (that and the combination that Lazio was from LI) here numbers in Nassau & Suffolk were a good 12 to 15 points below Gore's totals here. Even if Pirro didn't implode Clinton would have won LI easily this time, she will get well over 60% & possibly approach Schumer's 71% (though I see her in the 65-68% range. Anyway you really can't make much of Clinton not performing as well as Gore did in the state in 00 as nwhy she won't be a good national candidate, their were issues that held her vote total down that no longer hurt her.
