In just a week, the GOP will finally hold all the reins of power at the federal level.  Donald Trump will be sworn in as the 45th President of the United States.  In the Capitol Building, he can expect support from sturdy Congressional majorities.  In the states, the GOP is historically strong and remains set to enact numerous conservative policy priorities from Idaho to New Hampshire.

While it might seem counter-intuitive to celebrating, January 20th will also herald something else.  The beginning of the end for control for the GOP.  History is pretty clear on this point (with a few exceptions), once a party achieves total power they will begin to lose it.

More often than not the downturn begins quickly.  First, marginal members break from the party’s Congressional coalition.  Members worried about the midterm than form a de-facto internal opposition, believing that the status quo is preferrable to change.  Incumbent parties tend to retain the White House for another four years.  But the opposition party tends to retain a significant footprint in government.  Combined with the second-term Presidential midterm doldrums the opposition party is often well placed for a comeback in the open-seat Presidential contest.

If you look back far enough you can find exceptions to this rule of course.  The GOP maintained dominance after the Civil War due to the power of the Northern vote and Reconstruction.  The Great Depression brought untold pain and FDR was able to command a cult of personality and improve the economy.  Outside events like WWII also made him a war time President and a popular one at that. Even so, the GOP had periods of success under FDR including 1938 and 1942 where they made major gains in Congress.

More recently, JFK’s death in 1963 created tremendous goodwill for LBJ and Democrats.  Combined with the party’s strength in the South and a weak GOP opponent, Democrats dominated 1964. Even President Bush broke this trend in 2002 when his party gained full control of Congress (though 9/11 had much to do with it).

Yet, for the most part, this boom and bust cycle for the parties has been the dominant theme for over 200 years.  Parties are much better at gaining power. They are much less successful at holding it.

It is not hard to see why.  Put simply, it is hard to govern America.  Primarily, this can be attributed to three factors.  Some the party has control of.  Others, not to much.

The first is our electoral system.  America is an extremely diverse nation (just ask Democrats hoping this helps them).  Yet, we only have two major political parties.  On the surface party coalitions might seem homogenous but they are quite hetereogenous.  To win, parties often have to span class, racial and social divides.  The opposition party knows it has a steady base to draw from and thus seeks to poach marginal supporters from the governing party. Democrats did this with great success in 2006 and 2008 and Republicans did it two years later in 2010.

Secondly, our system intentionally makes it hard to govern.  The Constitution distributes power across multiple jurisdictions, the states, the courts, and Congress.  It is impossible to make all these entities coordinate their efforts to implement promises made on the stump.

This is a benefit of our system because it requires broad consensus to be reached before major changes are made.  Preaching bipartisanship on the stump sounds good for a candidate, but incremental change is not what the base wants.  Thus, candidates make broad promises in the hopes of getting elected. But, often, they fail to deliver.  The opposition is always more than willing to be telling voters only they can make government better.

Lastly, external factors often shock our system.  Wars, recessions, riots, racial tensions, etc. are all common in the annals of history. Recently, we have seen this with the Recession of 2008 and Ebola crisis of 2014.  Voters don’t always blame the incumbent party for external events.  Sometimes it benefits them.  Just ask George Bush in 2002 and even 2004. But, for the most part, voters take out their annoyance on the governing party.

I would be remiss if I did not mention sometimes individual candidates come about that are able to ride the waves of these variables.  For example, FDR was elected with strong majorities and enacted many policies that last to this day.  Jimmy Carter, elected in the wake of Watergate, was elected with similar legislative assets and squandered them.  Obama went the same route as Jimmy Carter in the span of two years.

Historically, even gifted candidates suffered setbacks.  FDR’s Congressional majorities were crushed in 1934 and 1938.  In 1946, a bipartisan coalition of conservatives and Southern Democrats held back major liberal legislation until 1964.

Today, it is even harder for incumbent parties to hold power and enact major changes.  The rise of partisanship means the opposition, is, well, more oppositional.  The self-sorting of the parties along ideological and racial lines means major changes tend to benefit only a few groups and anger others. Judicial appointments and rulings are now viewed along ideological and partisan lines.

Considering this, Republicans would do well to implement sweeping changes while they can.  Repealing the ACA, tax cuts, regulatory reform, all will involve trade-offs and likely not satiate voters demands enough to earn their votes.

The best example of this might be Obama and Democrats.  In 2009, Democrats had a filibuster proof majority in Congress and dominating majorities in Congress.  Though the party passed the Stimulus early and the ACA, it took over a year to do so.  Cap and Trade and Immigration Reform were killed before they even came up for votes in the Democratic Congress.  The result was a bloodbath in the midterms.

So Republicans, act quickly if you want to enact sweeping changes.  You don’t have much time.