I am a former libertarian Republican who has since become an independent for one simple reason: The Republicans have tended of late to take positions on issues which run contrary to the facts, and not coincidentally, the established authorities on those subjects. I am not aware of the Democrats doing anything akin to that.
After all, most political issues are not decided as factual issues. They are far more related to our personal moral and valuation systems, because they almost always involve a tradeoff of this consequence vs that consequence. However, to make good value judgements, we still need a good grasp of the facts so we know exactly what we are valuing over what. To choose between products we need to know their prices. So ignoring the facts is going to lead ultimately to bad politics, and that is what I see the Republicans doing, and that is why they have lost my support. Here are specific examples:
1) Evolution. Republicans far more than Democrats deny evolution and support creationism/intelligent design in a cultural battle that has gone on for decades and continues to this day. It also makes the United States somewhat of a laughing stock in the world. Note this survey taken of acceptance of evolution by nation. The United States scored better only that Turkey.
Yet every major scientific organization around the world, practically every scientist in the relevant fields (biology, geology, paleoanthropology, etc.) accepts evolution. The evidence supporting it is overwhelming. Yet Republicans deny it, against the entire world.
2) Global Warming. The Republicans once again stand alone in denying the science. No, the case is not as conclusive as it is for evolution, but it is rapidly getting there, and the pattern of denial (moving the goalposts) is very similar to what we see with the evolution deniers. First they claimed the earth wasn't warming at all, then they granted it was warming, but waved it away as part of a natural cycle, now they grant that the warming is greater, but not necessarily caused by humans. Yet the evidence keeps building, as the world's scientists now say it is 90% likely that humans are a major cause of the warming trends.
So my challenge is: show me something akin to this on the Democrats' side. I'm not interested in matters of philosophical opinions, moral systems, or value judgements. I'm talking about a position the Democrats take that, like the Republican positions on evolution and global warming, run counter to practically every fact and the opinions of every scientific institution dedicated to studying these things.