Were past VP choices net positives or net negatives for the ticket?

[Dr. Cynic]

1960: Johnson was a big positive while Lodge brought nothing to Nixon.
1964: Humphrey was a helper while Miller was really too unknown to be either.
1968: Muskie was a big helper. Agnew probably hurt. LeMay also hurt.
1972: Agnew would still be a negative as was Shriver, though it was hardly his fault.
1976: Mondale helped and Dole hurt.
1980: Bush and Mondale helped. Lucey was a drag on Anderson.
1984: Bush helped and Ferraro hurt.
1988: Quayle hurt and Bentsen was probably a huge helper.
1992: Gore helped while Quayle and Stockdale both hurt a lot.
1996: Gore and Kemp both helped.
2000: Lieberman and Cheney both hurt, in my view.
2004: Cheney hurt and Edwards eventually hurt.
2008: Biden may have helped a little bit while Palin hurt the ticket a lot.

[Dr. Cynic]

1968: Agnew helped and Muskie hurt, LeMay hurt a lot.

This is backwards. Muskie greatly helped Humphrey's campaign and even would allow protestors to take the podium to air their views. Historians agree that the choice of Muskie was a good one. Agnew was a drag on Nixon. Not just politically, but Agnew was a gaffe machine and made Nixon look bad, especially in 1968 when the Democratic ads tore at Agnew's image.