Note that this is a big one, so wait for abortion stuff down below.
One of the differences between the GOP and the DNC is that GOP routinely uses false arguments and abandon them left and right, while the DNC routinely sticks to it's real arguments unless an immense amount of proof shows them wrong. Conservatives are loyal to the program, changing arguments at will, while liberals are loyal to the argument, changing programs at will.
This is why conservatives prefer money saving light bulbs that use less energy but do NOT save the environment over money saving blights that use less energy and do save the environment. (source)
You see, unlike conservatives, liberals actually put forth their real
arguments to support themselves. If they are proven wrong, they change
their mind. But it takes a LOT of evidence to do so. Liberals come from a science background and science takes solid, thorough evidence. Conservatives on the other hand are quite willing to suddenly change their arguments but keep their mind, even when faced with relatively weak counter-claims.
This leads to some confusion. Conservatives think Liberals are far more hidebound than they really are, because the liberals keep sticking to their original arguments even after the conservatives think they disproved them. The problem is conservatives often have no idea how much evidence it takes to actually disprove an argument. Liberals think Conservatives are far more hidebound than they really are because they abandon their old arguments that they never truly believed in. Note this is not a 100% thing, more like a 55%/45% thing. There are exceptions - it is a generality, not a rule.
A prime example of this is the violent video game debate. Conservatives want them banned because they don't like them and think they are immoral. They put forth badly crafted theories that claim they cause violence. Liberals look at their studies and laugh at how poorly done they are. The conservatives sit in wonder thinking 'what will it take to convince the liberals', without having any idea of how ridiculous their studies are (outright confusing correlation with causation).
Simultaneously liberals try to tax sugar drinks, so the conservatives get all upset about 'excess taxes'. But that's a fake issue - they really care about personal freedom. So when the liberals switch from taxing sugary drinks to outlawing them, the liberals are so confused about why the conservatives don't like the new idea to outlaw them as opposed to tax them.
This dichotomy is mainly caused by the nature of the political parties. The word liberal originally meant in favor of progress, while the word conservative originally meant in favor of the tradition. As such, Liberals can easily abandon bad ideas and move on to new good ones. But Conservatives can't do that, because the new traditions are the old liberal ideas. Conservatives have a choice - either stick to your old ideas with new arguments, or accept the liberal ideas of the previous generation. Eventually they do make the switch to the liberal ideas of the previous generation - but it takes a generation. The old conservatives die out/retire and new conservatives that have adopted old liberal ideas move in (i.e. race-blind admission to universities is a prime example.)
Another reason why this happens is the core support systems.
Conservatism/traditionalism all have strong support among religious people. Religion is about faith and loyalty, so this core value has become central to conservatism. In a loyalty and faith based system, you keep your truth hidden and put forth many arguments that you may not care about.
The problem with a faith based political system is that it tends toward sudden dramatic shifts. There is no middle ground, to quote a conservative "You are either with us or against us." Hence the concept of the "Republican In Name Only." If you disagree just a little bit, you don't belong and are 'other'.
Liberalism is however founded on a more scientific thought process. It is about making things better, not accepting things as they are. As such, it needs discovery and tests, and sometimes negative results. At the heart of liberalism is a scientific method, not faith. It also requires a lot of significant evidence, thoroughly backed by science to disprove. This makes it a little bit more accepting of moderation, changes become gradual, not sudden shifts.
This is something conservatives never understood - they put together a tiny
amount of evidence, build it into a mountain and are shocked that the
liberals laugh at their molehill. Simultaneously liberals stand in dis-belief as conservatives bring up new arguments for clearly dis-proven political ideas.
This has certain implications about how progress happens.
First of all, again there are certain exceptions. The Abortion argument will never truly be won by either side. It will continue to be an issue for the foreseeable future. As I have said before, Abortion is different - it is not a scientific issue. Most of the other issues are. It is theoretically possible to scientifically determine if gay marriage hurts regular marriage. A massive double blind experiment could prove it either way. Not so for abortion.
I am NOT saying that the pro-life or the pro-choice's reasons are religious. I am saying that the question itself comes down to when an embryo becomes a person and THAT is at best a philosophical question, totally unanswerable by science. No amount of studies will ever prove the answer either way. As such, pro choice can never be proven wrong, and the pro-life people will never abandon their core belief.
Only God can tell us who is right or wrong about abortion. No studies can ever tell that. Instead we are stuck arguing about what should we do when we don't know.
One way to summarize their arguments is:
Liberals say "We don't know if it is a person and the only claims for it are religious, so that makes it a freedom of religion issue and you can't force me to believe your religion. QED abortion is legal."
Conservatives say "We don't know it's not a person, and no reasonable person can take the chance that our beliefs (religious or otherwise) are wrong. Thus any sane government forbids abortion."
Abortion is an example of what to do when we can't know the right answer.
But this differs from 99% of the other political arguments out there.
Most other political arguments can be proven. Unlike abortion, eventually we will find out the truth, it just may take a long time. Battles about drugs (Marijuana legality), Marriage, economics, etc. can all be proven with decades of studies. When they are proven, one side wins. When Conservatives are right, they need to painstakingly prove with impeccable science. When they do this, liberals cave in. It might take 2 years, it might take 40.
But when Liberals are right it takes a very different path. It needs to build up in a crescendo, slowly building strength among liberals, being repeatedly demonstrated to conservatives till a large majority laugh at the ridiculously, patently false ideas held by the old guard. It usually takes at least 20 years to get the laws passed. They need to wait for the old conservative guard to retire and the new ones to take over.
It's what happened with a federal banking system (from the early 19th century), the gold standard, social security. We pushed it through legislation, tested it for decades then watched the conservative opposition die out. That's what is happening now with marijuana and gay marriage. Give it another 10/20 years and these will cease to be issues. Not because the liberals will convince the conservatives, but because the older conservatives will retire/die off.
Of course, this means that before that happens, their will be more ridiculous scenes of conservatives believing obviously false ideas. Slowly they will realize that no one else agrees with them. It happened with racism, rape, and Social Security. Now it is happening with gay rights and marijuana.
Note this is not a 100% thing. There are liberals that still believe in Communism - but none of them hold a national elected office. (Despite the lies spread about Obama).
Also certain issues will not die, but simply slowly weaken. Take Black/White Racism. In the United States it was created in order to justify slavery. It started back in the 17th century, but was strengthen by slavery until the mid 19th century. When the good guys won the civil war, the real war against Black/White Racism began. It took almost 150 years to get a black president, and Black/White Prejudice still struggles on, half-dead but still surviving.
That battle had to be won repeatedly. Voting rights, educational rights, marriage rights, fought slowly. But real progress was made. Not like abortion where things swing back and forth.
Other wars were much shorter. You don't hear people claiming that the irish aren't 'white' anymore, but they used to be considered a separate race, with racist laws hurting them.