Democrats haven't changed any rules... they've been strictly following the 60 vote super-majority rule in the Senate even though Republicans have been abusing it.
I am talking about when Kerry was running for President and Romney was Massachusetts Governor.
The Democrat controlled State Senate in Massachusetts changed the law, in the event that Kerry won the Presidency, the State Senate took away the power of the Governor, at the time Republican Romney, to appoint a new Senator. Later, the Democrat controlled State Senate, when it became clear that Ted Kennedy would not live much longer, they changed the law again, allowing the Governor, at the time Democrat Patrick, to appoint a new Senator.
That is most definitely changing and manipulating the law whenever it suits the Massachusetts Democrats narrow minded and self serving political agenda.