Sometimes it is hard to tell the difference, professional politicians tend to resemble each other, getting elected is a process that leaves marks. If you believe you have to go along to get along, then you go along with a lot of stuff you may not really belive in.
However, I recommend the party of Lincoln (ended slavery for whatever reason, although he did suspend habeus corpus) and Teddy Roosevelt (antitrust, first national parks) over the party of Jackson ("the supreme court has made its decision, let it enforce it." the trail of tears--Cherokee indian removal) and Franklin Roosevelt (pack the court, 4 terms). Yeah, each party also has some not so great presidents landslide Lyndon and Nixon for example, but the country is often better off with Republicans in charge because they want to change less.
Politics is supposed to be the art of the possible. When ideology gets more important than running the country (or whatever political unit is under discussion) bad things happen. The worst case, probably was the Civil War (oops, the War of Northern Agression). If you go too far, and take out the incentive for the other side to get its say, and chance to run things next election, they take their marbles and go home, and you might get another revolution. Our historic advantage has been a relative absence of coups, and popular uprisings and a relatively stable government. Maybe you can only have that when the choice is between tweedle dee republican and tweedle dum democrat. Third party ideas tend to be taken up by the mainstream parties so they can keep being elected. This may not be that bad a system.
I read somewhere, if you want to enjoy them, don't watch sausage and laws being made.
