I'm sorry, the ideological classification of vice-presidents that you have posted is completely absurd. How exactly is John Nance Garner the most liberal vice-president on that list?
What part of the data do you take issue with? Those ideology scores aren't just pulled out of thin air. They're DW-NOMINATE scores which are used in political science as the gold standard for comparing the ideologies of legislators. Garner's score there is an objective measure based on his voting behavior relative to the rest of his congress (taking into account every roll call vote in a given congress).
DW-NOMINATE does a very poor job of comparing people from different eras. Also, they may label their axis as being Liberal-Conservative, but it really is more of a Democratic-Republican axis than Liberal-Conservative.
