@Revan
Political philosophy isn't something I've read much about but I'll try and roughly summarise what I like about McTurtle and partisanship. And obviously I'm simplifying
a lot.
There are 2 ways to look at him and his politics.
1. Politics is a battle of ideas. Mitch and the GOP believe sincerely that the results of market forces in terms of income, healthcare, housing, etc are the most desirable outcomes. Human creativity can only be unleashed in an economically free society - regulations destroy the core of that. They reward the best and brightest, or they reward the people the ones most suited to wealth and power - either way they create a justified, sound hierarchy.
They believe in conservative social values. They believe that the past thousand years of human civilisation have shown that it is best to stick to what we know, (and/or) that the status quo is good, (and/or) that lower orders demanding change leads to violence, chaos, and disturbing what nature or god ordained, and that what hierarchies we see along gender or race or wealth lines are there because of aptitude/skill/fitness. The more aristocratic American revolution succeeded where the more radical French revolution failed, precisely because they recognised that striving for equality is a fool's errand - thus the US constitution is a sacred document especially when it meshes with their other beliefs.
They believe that ordinary people left alone would tend to devolve into violence, that you need strong states to organise them, and you need these states to safeguard and expand their own dominion, otherwise other states would take over.
In this case, it makes no sense to have a high tax rate on rich (better, more capable) people; it makes sense to spend on military and not on healthcare (you need to defend national interests, the market will efficiently allocate treatment to those who need them). Abortion is a way for women to escape the consequences of their actions, an artificial invention to liberate them at the expense of the stable patriarchal family which western civilisation has been built on. And it violates the teachings of the Bible, another pillar of western civilisation. How can this revolutionary murder be supported?
So why should he compromise, when it would weaken society by helping less capable people, encourage violent revolts that overturn the natural, correct, order of things?
2. Politics is a battle of interests. Mitch is nobody, he is just a representative of the groups that fund and organise for him and elect him. His job in the senate is to do what he can to further them. These interests want less environmental regulations because they want to grow. The owners of these companies will be dead before global warming hits, so it is important that greenhouse regulations not interfere with their work. They dislike having to deal with workers, so they want to restrict union power. They believe deeply in the Bible and therefore no abortion. They need to manufacture and sell weapons, hence he should lobby for more military money and more wars.
Why should he compromise?
And then you look at Chuck Schumer. Based on his actions, I have no idea what his guiding philosophy is, or which interests he is beholden to.
He takes money from Wall Street and from teachers' unions. What will be his stand on govt funding for private schools that discourage union formation?
Hillary got millions from the oil industry, and millions from the Sierra Club. What was her stand on fracking?
Obama said he believes all wealth is socially generated, never by a single person. He also said that capitalism is the motor of prosperity. What is his stand on regulations?
So how can the Democrats fight the Republicans, when they themselves have no clear constituency (they try to be the party of Wall St, Silicon Valley, minorities, unions, and the environment) or clear motivating ideas? Of course they will always compromise, while Republicans will have a clearer picture of what they want.