Arlen Specter Switching Parties, Toomey's run caused him to run in Democratic Primary
The LA Times has this:
Reporting from Washington -- When a Senate Republican left his party in 2001, elevating the Democrats to majority status, one member of the GOP was especially vocal about his displeasure: Arlen Specter.
Specter said then- Vermont Sen. Jim Jeffords' decision to become an independent was disruptive to the functioning of Congress. He proposed a rule forbidding party switches that had the effect of vaulting the minority to majority status in the middle of a congressional session.
"If somebody wants to change parties, they can do that," Specter said at the time. "But that kind of instability is not good for governance of the country and the Senate."
Now it is Specter switching parties, proclaiming himself a Democrat. While the move won't throw one party out of power, it could potentially hand the Democrats a 60-vote majority and deprive the GOP of the ability to block legislation through a filibuster.
Eight years ago, Jeffords' decision cost Specter his chairmanship of the Veterans Affairs Committee. Specter said at the time that he wanted the rule change to prevent a party switch that could decisively swing the balance of power in the Senate overnight, disrupting U.S. domestic and foreign policy. . . . .