On July 16, 1999, JFK Jr. died when his single engine light airplane crashed into the Atlantic Ocean off the coast of Martha's Vineyard. His wife, Carolyn Bessette, and his sister-in-law, Lauren Bessette, were also killed in the plane crash. What if the 1999 plane crash never occurred and JFK Jr. ran for and won the open U.S. Senate seat from New York in 2000?
IN OTL, Senator Moynihan announced in November 1998 that he would not be seeking re-election in 2000. New York Democrats sought a high profile figure to run against the likely Republican candidate, Mayor Rudy Giuliani, and approached First Lady Hillary Clinton in late 1998 about running. President Clinton was not too keen on the idea of Hillary running for the US Senate in New York State in 2000.
Unlike Hillary--a carpetbagger who never lived in New York State before purchasing a home there in autumn of 1999--JFK Jr. lived in the New York City area for much of his life. As an adult, JFK Jr. lived in New York almost continuously from 1984 until his death.
Polls in 1997 showed that 65% of New York State Democrats had a favorable view of JFK Jr. Hillary did not announce the formation of an exploratory committee for her Senate run until July 7, 1999, less than 2 weeks before JFK Jr.'s death in OTL. He was reportedly interested in running, but stepped aside for his friend Hillary.
If JFK Jr. had announced in late 1998 or early 1999 (as the Clinton impeachment scandal was still playing out) that he was definitely running before she made her own decision, then Hillary Clinton may have stayed out of the N.Y. Senate race altogether.