This State Department cable from the American Consulate in Jerusalem discusses the rivalry between Hamas and Fatah during the intifada. The document's conclusion:
HAMAS WILL NOT SOON REPLACE FATAH AS THE DOMINANT POLITICAL FORCE IN THE WEST BANK AND IS UNLIKELY TO FORCE AN OVERT TEST OF STRENGTH. BUT, AS NOTED REF A, IF FATAH IS UNABLE TO TRANSLATE THE INTIFADA INTO POLITICAL GAINS, THE INFLUENCE OF HAMAS COULD GROW, ERODING FATAH'S LEADERSHIP AND THE COHESION OF THE UPRISING.
Read the complete cable here.
Source: U.S. State Department