History of Party Control of US Congress

Apologies for back to back political posts, but it seems to be all that anyone is talking about until tomorrow is over.

Many political scientists argue that "realigning" elections happen in the US about once every 35 years.  In these elections, there is a political paradigm shift and a redivision of the electorate along new party lines.  Generally these realignments happen in conjunction with a major historical friction like the Civil War or the Great Depression.

In American history most agree that realigning elections happened in 1828 (Jackson), 1860 (Lincoln), 1896 (McKinley) and 1932 (Roosevelt).  There's some dispute about whether one happened in 1968 with Nixon or 1980 with Reagan, although I tend to believe that we're still in a system representing the vestiges of the New Deal Coalition (1932).  

Either way, it can be argued that the US political system is long overdue for a seismic fundamental shift.  I think that growing interest in Libertarianism against the backdrop of high public debt and extreme monetary policy is indicative of a bubbling change in the electorate, but while these ideas have begun to influence the conversation (e.g. through the tea party and Ron Paul), we're not at a paradigm shift quite yet.

For some perspective, below is a chart showing the history of political party control of congress.  The exact political epochs are debatable from historian to historian, but I based the labels in the graph loosely on the five party systems defined by wikipedia.

Click to Enlarge.  Third Parties and Independents Excluded.  Data source: Office of the House Clerk