If reforming capitalism could work, even a little, then Franklin D. Roosevelt's comprehensive reforms of capitalism in the 1930's and 40's would have worked. They have not, and it seems entirely implausible that we can do better than his reforms while still preserving capitalism.
We can determine empirically that FDR's reforms ultimately failed, and there's a theoretical understanding as to why they failed. Empirically, we have seen since the 1970's a steady decline in the wealth, power, and standard of living of the American working class — in comparative and absolute terms — even as the overall wealth of the nation has increased by an order of magnitude. We have seen Democratic party administrations cheerfully undermine the foundations of reformist capitalism: especially Clinton on welfare and the regulation of finance capital.
The theoretical reason is that reformist capitalism is inherently unstable. The primary dialectic within the capitalist class under reformist capitalism becomes a conflict between those who would preserve existing reforms and those who would undermine them. Individual owners of capitalism have a strong incentive to override or evade reforms. It takes just as much political will to preserve existing reforms as it does to erode them. Therefore, any temporary failure of will to preserve existing reforms will result in some erosion; when the will returns, it will be directed towards preserving those reforms that remain, not regaining lost ground.
The dialectic within the working class mirrors this bourgeois dialectic. The capitalist reforms distribute benefits to the working class unequally: the dialectic within the working class thus becomes a conflict between those who have achieved more benefit and those who have achieved less or none. Again, we see a ratchet effect: it requires as much political will to preserve one's benefits as to lose them, and any transfer of benefits from one portion of the working class to another inevitably loses ground overall to the capitalists.
(There are, of course, a few positive gains made here and there to living standards for the working class. But for every gain there are ten losses, and the overall trend is clearly downward.)
This ratchet has — with the deregulation of finance capital — begun in the last decade to hit the professional-managerial middle class. Even the most highly skilled professionals are subject to relentless market pressures to reduce their economic participation to bare survival.
We're still far from the bottom, but with the debt crisis, the enormous and still growing unemployment crisis, the ratcheting-downwards is picking up speed.
At best, with adroit skill and iron will, President Obama and the Democratic party government can slow the decline, and perhaps pick up a couple of modest gains, perhaps some half-assed "universal" health care which will slow, but not stop, the inclusion of access to medical care to the "big three" ways (rent, interest and profit) the capitalist class exploits the workers' surplus value.
We can talk all we want about "principles" and "common sense", but what's happening is (as always) a dialectic of interests: class interests, intra-class factional interests and individual interests. Analyzing the present circumstances as a dialectic of interests and the power to realize those interests leads directly and inexorably towards the conclusion that the wealth, power and standard of living of the working class, professional-managerial middle class and petty capitalists (small-business owners) will decline until they find the will to resist in common cause.
Once conditions have declined to the point where the "lower" classes find the will to resist, conditions will reach rough parity, and very small differences, especially in leadership, will have enormous effects. The outcome of that class struggle will depend in no small part on who is stronger: our Hitler or our Lenin. (We will have no Roosevelt; material and political considerations entirely preclude reformist capitalism.)
In the long run, socialism leading to communism will eventually triumph — at least if we don't kill ourselves off first. Communism is just better; sooner or later everything will come together and we'll take the next step in civilization. But, as Keynes famously noted, in the long run, we're all dead. The question is what's going to happen to us and our children, living, breathing, thinking, feeling human beings.
I'm not particularly optimistic about how things will turn out in the United States. I see us more in the light of post WW-I Germany 1918-1919. (See Sebastian Haffner's excellent book, Failure of a Revolution.) First, conditions will deteriorate within the next 4 or 5 years until much of the working class (and the unemployed class, a novel feature of modern post-industrial capitalism) are in conditions of semi-starvation. Unrest will develop, but the working and unemployed classes will unwittingly support leaders and politicians who will betray them. In the interests of preventing a revolution (and not coincidentally preserving their own privilege), "leftist" politicians and leaders (i.e. supposedly "progressive" Democrats) will covertly make common cause with the right-wing bourgeoisie, who will unleash the well-armed, well-trained Christian fundamentalists to "restore order", just as the Social Democrats of post WW-I Germany unleashed on a rebellious population the rightists who would later become the Nazis.
Can we pull back from the brink of Gilead? Perhaps. But the people by themselves cannot do the job on their own. It's an unfortunate but ineluctable truth that while historical crises are caused by broad, material factors, the outcome of every crisis is sensitively dependent not on the general state of the people but on the qualities of the classes' and factions' leadership. (Else Germany would have succeeded in a socialist revolution and Russia and China failed.)
If the communists find leadership combining the theoretical brilliance, practical and organization skill and energy of Lenin, we stand a fighting chance. If the fascists find leadership combining the theoretical brilliance, practical and organizational skill and energy of Hitler (and there's no doubt that Hitler, despite being a truly horrible person, was brilliant, skillful and energetic), we're well and truly fucked.