Have Nancy Pelosi and Hillary Clinton duke it out for the Democratic nomination in 2008, POD 2000.
In fall 2007, a terrorist attack kills the President and Vice President, and Senate president pro tempore Robert Byrd dies of a heart attack when he hears the news, leading to Pelosi's inauguration as President of the United States.
She announces an intention to run for the Presidency, but current candidate Hillary Clinton has no inclination to defer.
So Pelosi is being LBJ to Hillary's RFK? That's interesting, but Pelosi was hardly known in 2004. Sorry, but I'd like an open fight in 2008.
By the way, the POD was 2000.
Lyndon Johnson would not run for a third party, he knew Bobby had defeated him. You should read their last conversation before his murder- LBJ basically said "I never hated you, this was a misunderstanding." After all the anti-RFK venom, LBJ deserved every bit of that. And even if he strong-arms the convention, RFK becomes POTUS in '76- if Sanders can win the '70 primary. But that was unfortunately not to be in OTL. Going back to Pelosi v. Hillary- but if you want to know, read Mutual Contempt, which is excellent.