This picture tells the story:
The percent of seats of the House of Representatives, the Senate, and the Presidency are plotted, starting in the year of the relevant election. I arbitrarily started at 1900.
The solid black line shows the Senate, the dashed black the House, and the solid blue the period of Democrat presidents (again, with the election years as the reference points).
To handle the odd third-party seats, the percentages were calculated based on the size of the Republican caucus in each house.
It is important to examine the percent of seats and not just the majority because, naturally, the closer a majority party is to the 50% mark, the more they are willing to compromise in the direction of the other party.
What might seem surprising is the extent of agreement between the House and the Senate: it is rare that majorities in both houses do not agree.
A glance tells that we have spent the majority of time with a Democrat-controlled legislature.
The forces that gave rise to the percent of Senate seats has the most correlation with which party wins the Presidency. This is probably because of the slower turn-over rate of the Senate as compared to the House.
Whichever house you consider, the fickleness of the American public is obvious. Even though one party (usually Democrat) controls a house, the share of seats oscillates with regularity, especially in more recent years. The pulse of the Senate is almost exact.
Up until roughly 1954, the public was more trusting of forming majorities in the House, Senate, and Presidency. That is, if the House and Senate were Republican controlled, so was the Presidency, and vice versa.
Thereafter, only Democrats controlled all three, or there was a mix. The exception is the first part of the Bush Presidency. Also during this time, Republican Presidencies correlated strongly with losses in Democrat seats in both the House and Senate (this is losses, not loss of control).
It is well to emphasize that the makeup of the Legislature and the Presidency does not imply an agreement between the government and a majority of citizens. A history of the recent welfare/entitlement health law proves this.
How to combine all three parts of government into one measure? There is no formula, and we have to rely on subjective judgment. No matter what we devise, missing completely, of course, is the third branch of government: the Supreme Court. This picture shown here, then, is necessarily incomplete.
The method used here is a simple average of House, Senate, and Presidency (Republicans score “100%” of the available seats with a Republican president). This is imperfect. Since it is the House and Senate that have control of money, perhaps Congress should receive more weight than the Presidency.
But it is the President that suggests a budget, and there is always significant anchoring to and adjustment of that offer. Plus, the President has a veto, the knowledge of which influences the behavior of Congress, particularly when the President is of the opposite party.
And then the Presidency is of much more importance to foreign policy, particularly in times of war. All these facts led to an equal weight.
We can all this index the percent Republican control of the country. It is the green line.
Except for the extra dose of Democrat during the FDR years, our fickleness is again evident.
Or perhaps “perpetually unsatisfied nature” is a better term than fickleness. The duration of control is mostly set by the rules governing our election cycle. But the bouncing back and forth is entirely due to us. One year we gladly agree that we should be awarded money from the public coffers, only to find that we aren’t happy with the decrease in our paychecks caused by the new entitlements.
But is that all? Maybe oscillations are the natural response of a democratic citizenry to the excesses and idiocies of the controlling party. Before politicians of one party become too powerful, we toss them out. And we often do so certain sure that the other party will be—this time—our saviors.
The 2010 elections are approaching. Crude extrapolation from recent trends—and ignoring all external factors—suggests Democrats will lose seats but retain majorities in both the House and Senate. However, these same extensions put a Republican in the White House in 2012, with a Republican Senate and Democrat house.
We can call these predictions the naive forecast, based simply on the data.