If Democrats are concerned about one-party dominance in Washington - and further conservative consolidation through Supreme Court appointments - they can look to their own history for a reminder of how difficult it can be for one party to gain an unbreakable lock on power.
In 1937, when Franklin D. Roosevelt began his second term, Democrats were at the top of the political food chain.
The GOP held only 89 seats in the House and 16 in the Senate. But that was not enough for FDR. Angry that the Supreme Court had invalidated much of the early New Deal, he tried to pack the court with up to six new justices. But his own party, as well as the public, rebelled. The plan failed, greatly weakening his second-term influence.
Two points come to mind from this stroll down history lane: One is the danger of presidential overreach, and the other is that a majority in Congress does not guarantee party unity.
These lessons can't be lost on President Bush's political architect and history buff, Karl Rove, even as he talks up a "broad" mandate and his boss insists he now has the political "capital" to push his agenda full force.
Yes, the Republicans widened their margins in Congress, but they are by no means filibuster-proof in the Senate. That more deliberative body has a contingent of moderate Republicans, and both chambers contain GOP lawmakers unhappy with the president on such issues as the federal deficit and postwar Iraq.
These political considerations should serve to calm Americans nervous about a greater power imbalance. But more reassuring should be the Constitution itself.
The Founding Fathers designed the three branches of government to make it as difficult as possible for one person, faction, or institution to roll over another. Even if one ideology could also permeate the judiciary (and don't forget those justices who turned out to vote differently than expected), checks within and among the three branches regularly act as a brake.
The president, for instance, has four years ahead of him, but will eventually operate as a lame duck. This is not to conclude that the president's agenda will fail, but to point out that many factors work against extremes in government. Differences between House and Senate rules make it difficult for GOP bulldozers like House Majority Leader Tom DeLay to ram an agenda through the Senate. Remember Newt Gingrich's "Contract with America"? It sailed through the House but crashed in the Senate.
That's not to pretend that America's checks and balances work perfectly. Of particular concern is the weakness of congressional oversight (for example, over the intelligence community), and of voting district gerrymandering that make House incumbents virtually untouchable.
But history and the Constitution remain on the side of sustaining political moderation in Washington.