Yes, they have.
No, they haven't.
At least to a degree. I believe a few have changed it completely, but I can't think of any examples right now.
Well i started out my high school as a liberal democrat, then a lot of my friends where conservative republicans so I naturally gravitated to that ideology. But after hanging out with my conservative friends I started to realize that they where wrong on numerous things like the drug war and foreign policy. So I transitioned into a independent thinking I was the only one of my type. then I discovered the libertarian party in 2012 when i saw Ron Paul debating.i have now developed a strict believing int he constitution and i believe that the 2 party system just represents the same people, the rich.So yeah, debate turned me into a libertarian
Very, very rarely.