The problem isn’t the Protestant Christian vote, it is the Catholic Christian vote.
If Catholics voted like non-catholic Christians, the left would dry up.
The Catholics remaining unAmerican is what the left sees as the keys to the kingdom of owning the future, it is why they fight for Catholic immigration and gave us the 1965 Immigration Act.
So the 75% to 80% of the population who aren’t Catholic never vote. Gotcha.
Longenecker is pointing out something which has been explained to you on multiple occasions by numerous posters.
"Catholics" who vote for Obama, for instance, have abandoned Catholic values and Catholicism itself. They have instead, adopted the prevailing values of current American culture. In what sense are they "Catholic" then?
They are not sustaining "the left". They are in fact, embracing a longstanding liberal ethos which predates the Catholic influx to this country and which is now approaching its end game. "The pursuit of happiness" to increasing numbers of modern Americans, Catholic, non-Catholic, agnostic and atheist, means the pursuit of unrestrained sexual gratification and the disposal of its unfortunate products in the form of abortion, for instance. Who are we to stand in their way? This theology is ancient and not dependent on fallen away Catholics for its propagation or continuation, although many have embraced it.
It should be noted in passing, of course, that Republicans have no solution to this problem. Anyone who thinks otherwise is deluded. They are, in increasing numbers, pining to join the Democratic cool crowd and are bending over backwards to show that they're not "homophobic" or "anti-women".
They are also at the forefront of America's current liberal cause de jour; the destruction of ancient Christian communities in the Middle East. Iraq's de-Christianization owes much to the last "conservative" in the White House.