The last time I checked Kerry's approval rating was something like 47-48 with 48 percent disapproving,
Wow, those ratings are HORRIBLE.
They certainly aren't great, but for a Democrat in Massachussetts are hardly dangerous. Conrad Burns had far worse ratings and still lost by only a point. Bob Menendez had worse ratings. Those ratings don't matter when the best you have is someone who lost by 20 points to someone more liberal than Kerry.
A Democrat could knock Kerry off in the primaries,
Why? Kerry's approval ratings among Democrats are still fine. Plus who's going to run against him? And incumbents only lose if there's a massive movement against them, either from the establishment (Bob Smith) or grassroots (Joe Lieberman). Neither one is going to go after Kerry. And note that with all things considered and everything the Democrats had against him, Lieberman still got over 48% in the primary. Kerry is NOT going to do worse than Lieberman.
However as we know this race leans Democratic for the general.
"Lean Democrat" is more than a bit of an understatement.
Kerry is not going anywhere. PERIOD.