Can’t see it having any more influence ITTL
than it did IOTL, as nobody had ever heard of Ms McKinney(including, I have to confess,
me) & therefore I doubt she’d bring more to
the table then whoever Nader did run with.
Nader would probably get more air time, and take a bigger bite out of Gore's vote, with McKinney being a more high profile progressive than LaDuke.
Ultimately the most Nader can be in 2000 is a spoiler for Gore, I'm pretty sure he wouldn't be able to crack 5% of the national vote in 2000, even with McKinney.