Catholics, and atheists vote liberal, it is the fact of American political life.
It is truly bizarre to blame liberal victories on the group that always votes against them.
What you call merely "numbers" are the facts. If you don't like liberal politics,then vote against the democrats, if you do, then vote for them, how do Catholics vote? How have Catholics voted always, with the exception of 6 times?
Catholic vote with a slight bias toward the liberals and Protestant vote with a slight bias toward the conservatives. But except for the Kennedy disaster. American Presidents have been all Protestants and the Protestant electorate is much larger, so the (for example) 45% Protestants that vote liberal are a bigger problem than 55% Catholics: they are more people.
Besides the country was set up by the Protestants. They therefore built in the liberal bias into the system. They wrote the Constitution; they voted for Protestant Roosevelt to create the New Deal and they voted for Protestant Johnson to cement the Great Society, America’s crippling welfare system. These two defections (over the course of three election cycles) of the Protestant electorate to the left were critical in the liberal slide of the 20th century. Now they should own the outcomes of their bad theology and unworkable social theories.
If you want to move the Catholic Church to the left, come join her. There is nothing that can possibly endear you to the Luther’s and Calvin’s theological fables, and you’ll be a part of true spiritual awakening of America rather than ones watching from the sidelines and tsk-tsking over things past.