“How many democrats viewed Regan as an alternative to Carter or Mondale”
You are talking about a totally different era and the majority of democrats were not so leftwing progressive at the time.
My brothers usually vote Democrat, but neither is a leftwing progressive by any measure. They are moderates. You are underestimating how unlikeable many people find the Republican Party. One of my brothers generally thinks the Republicans are against the little guy in favor of big business. That is why he voted for Obama (although he did vote for W. over Kerry). There are still some good, hardworking people sympathetic to many of our views in the Democratic Party. Their last remnants need to be broken free from the Democrats and that party can then become the pure party of Cultural Marxist progressives and their various dependent victim groups.
I think many democrat voters are not as left wing as their elected leaders are now. Look at the strategy they used to take the House on 2006. They ran as blue dog moderates but turned radical when they got in. Carter got elected by running as a moderate and fooling everybody about how radical he really was until he got into office. Reagan democrats were the people who Carter fooled. I suspect people like that are still around.