I like this comment that is on an obscure discussion board:
Why are Congressional Democrats so spineless but Republicans always so forceful?
Answer: I have often written about the basic nature of the two-party system, in which one party (in our society the Republicans) represent the interests of those who derive their livelihood from the proceeds of property, and the other (our Democrats) represent the interests of those whose sustenance is earned by the product of their labors or who for whatever reason may require government assistance to obtain such sustenance. The odd thing is that, while Republican leaders recognize this clearly, Democrats, both Democratic leaders and rank-and-file voters, AND Republican rank-and-file voters, seem not to understand this and get all confused by such extraneous matters of policy as social issues, environmental policy, and other specific matters, some of which have relevance to government policy and some of which don't.
By and large, those whose interests are unabashedly championed by Republicans tend to be wealthy and those whose needs would, on a level playing field, be defended by Democrats tend to live hand-to-mouth. Our system of campaign finance requires both parties to obtain the bulk of their funding from those whose interests the Republicans represent -- the wealthy. Wealthy people and corporations chafe under the horribly oppressive burden of campaign finance limits, feeling that they prevent from purchasing the influence over our elected officials that their wealth has earned them, while such limits are totally irrelevant to Democrats because most of us have to scrape and do without something we would otherwise purchase if we want to donate even as much as $50 to a presidential candidate. Democrats therefore cannot frontally assault the privileges of the rich because they too must court the rich for contributions or their campaigns will be starved of funds. Under our current system of privately funding our elections they have no way around this. Therefore, no matter how badly we need to reform the harmful and dangerous practices of such heavily moneyed and politically involved entities as insurance companies, energy companies like Exxon/Mobil, and banks and other financial institutions, their interests will invariably prevail because politicians of both parties are utterly dependent on the goodwill of these special interests if they wish to mount effective and well-funded campaigns for election or reelection.
This effect is far worse in the Senate because of its absurd method of apportioning power. A company like Bank of America could buy and sell North Dakota or Wyoming, along with the two Senate votes that carry as much or more weight as the Senate votes of California or New York.
This problem (well, it is a problem if you are not a "natural" Republican and/or a corporation), of course, will now get much worse in the wake of the Supreme Court's decision in Citizens United v. FEC.
So Democrats are spineless because they have got to mitigate the thrust of everything they do in order not to offend their natural adversaries on whom they depend for funding, while Republicans can behave forcefully because they have no need to court the good will of anyone other than those whose interests they naturally represent.
linkUntil the Citizens United decision is overruled one way or another, this dire situation has no other chance of changing.