The Democrats had the votes to exclude McCain but they wanted the Republicans in agreement to give them political cover. Helms refused. He was in the tightest race of his career, one that would go into the wee hours of the morning on election night. He didn't want to be seen as excusing a Republican and prosecuting Democrats no matter how innocent the Republican was. It was his refusal that forced McCain into the hearings.
Hey, he got the nom, it was his turn, he wimped, he lost. Now it's funny to watch him get a little energized about a campaign. He gets to fight a Republican!