It is increasingly difficult for politicians to please everyone in a country as diverse and large as the United States is. Conservatives support the idea that everyone works and pulls his or her own weight, while socialists want to tax the rich and support the poor therefore assuring that the people who fall into that category will always vote for them. Most people agree that they would like more leisure time to pursue hobbies and interests, but without working and having money to spend in that leisure time, I'm not sure how the country will survive.
Unfortunately, many of us have become so lazy that we would love a government who will pay our rent for us and forgive us all our bills...but that's just not how the world works. Someone has to pay for the debt. We must be more disciplined, live more simply, live within our means, and work for our meals and to pay our bills.
Two major themes that can go with this, from my view:
1) Widening dissatisfaction with the Bush Administration, from the tragic mishandling of the Hurricane Katrina response, to mounting casualties in the Iraq War, to the real estate, banking and stock market meltdowns of late 2008 led to people looking for something different. It changed the mood of the overall electorate.
2) A changing electorate, with greatly increased participation and involvement by young people and minorities, such that the overall political map looked much different in 2008 than in, really, any other election in US history. There was no real way McCain's campaign could have successfully responded to both that fact, and what I discussed in #1.
The American people are a very diverse group with equally diverse interests. Unfortunately, many pundits and posters try to categorize 308 million people as divided along simplistic and inaccurate lines such as Nazi and Socialist, rich and poor, hardworking and lazy. While it gives them comfort that their worldview can be expressed in such black and white, clear cut terms, they are nevertheless inaccurate generalizations.
I think the changes in political culture are changing from not so much what party are you representing but what are or can you do to help "me". Individuals are looking closer at what has or hasn't changed and I think are voting for change. This makes it incredibly hard on the incumbents since we can look at their past records on issues.
Whilst I think #2 is right in indicating the major shift towards tolerance as embodied in Barack Obama, it is also incredibly important to look at the Presidency of George Bush and his quite aggressive foreign policy, which still is impacting the United States now as they desperately seek to find a way they can withdraw from some of the conflicts George Bush led America into.
I will assume that you are talking about the political culture of the United States.
It is very hard to know what changes occured in a country's political culture when the time period in question is so recent. A person might have predicted things in 2008 (like that the political culture had turned away from the Republican Party) that look ridiculous today. So you must take all of this with a large grain of salt.
The major change in political culture between 2004 and 2008 appeared (in 2008) to be a major shift towards tolerance and "progressive" ideas. This was manifested in the election of a president who is half African American. Barack Obama did better among every demographic group than John Kerry did in 2004. This seemed to indicate a move towards more liberal ideas after the eight years of Pres. Bush's terms.
It is no longer nearly so clear that this was a true change in political culture. We will not be truly able to know how the political culture has changed until we more time has passed.