The big difference is that the Campaign Finance Reform Bill was a Republican Bill and President's never like to veto legislation initiated by their own party, even though it was McCain's pet project. However, with a Democrat controlled Congress pushing forth obnoxious legislation, I'm willing to be that he will have no such restraint.
47 of the 60 Yea votes in the Senate were 'Rats. 198 of 240 votes in the House were also 'Rats.
In short, it was not a Republican Bill, in spite of McCain's sponsorship, with Fiengold (RAT) as cosponsor. The House sponsor was Rep. Shays (RINO) CT and the only cosponsor was Rep Meehan (RAT) MA.
With 60 yea votes in the Senate and 240 yea votes in the House, a veto would not have been overridden (takes 67 votes in the Senate and 290 in the House)