Partisanship has taken over in our political system over the last twenty years. While most liberals would likely point to the election and re-election of President Reagan and then the election and re-election of President George W. Bush, most conservatives typically point to the election and re-election of President Clinton and (especially) the election of President Obama.
I do not think that it can be as simple as finger pointing at past (or current) presidents.
Some people point at the caustic and sometimes damning talk radio. Again simply blaming talking heads for the partisanship just does not fully answer the question as to what ended bi-partisanship. As long as there has been radio and television there has been someone using time on them to spread their particular view point.
There is a starting point, however, that can be looked at.
On June 1, 1980 Ted Turner premiered CNN to the American populace. It was the first of what become many cable channels that provided 24-hour news coverage. I am not putting the blame on CNN, however. The blame lies with the advent of 24 news hour cycles. There became a rush to be the first one to break a story.
On October 7, 1996 Rupert Murdoch launched the Fox News Channel and the race was on. For the first time channels were competing to put out political stories. Every political story was treated as a breaking news story worthy of Watergate proportions.
The talking heads who had long been relegated to radio stations (whether it be local or national) now had a truly national way to reach the masses. People began to be put into two camps. Instead of what was once a Democrat or a Republican not became a Liberal or a Conservative.
This country has largely been run from the middle of the political spectrum. Through 1960 there had really not been very many truly partisan presidents. The most notorious was Franklin Roosevelt. However, since that time we have had several presidents in their runs for office have affiliated with what is considered the base of their party.
After their election they have normally tended to run their office from the middle. George H.W. Bush did so as did Clinton.
President Obama has attempted to run from the middle but most of his policies either end up slightly to the left of the middle (which annoys Republicans) or slightly to the right of the middle (which annoys Democrats).
Many people have called the 2012 a historical election (mostly for partisan political reasons). I agree with them to an extent. Watching Mitt Romney completely change his beliefs (some which he held as late as two years ago) to placate what is considered the base of the Republican Party has been extraordinary. It will be interesting whether he will be able to pull himself back to the middle by the general election or if he will stay as far right as he has portrayed himself to be.
It will definitely be an interesting next couple of months.
Where we have seen the most partisanship in politics in Congress where politicians on both sides have continuously voted against issues that they once supported because it is what their party wanted them to do. It will be interesting to see if in November the electorate choose to stay with the partisans or elect a new group of politicians that will actually work together for the interests of all Americans and not the interests of the party or special interests.