The theory more or less states that domestic politics dictate foreign policy.
Incumbent is the argument that WWI was ultimately the result of European rulers seeking to turn attention away from domestic troubles.
I disagree, but that's not relevant to this discussion.
Now, this argument has been used in more recent contexts.
For instance: An argument says that Nixon, facing increasing pressure to speed up American withdrawal from Vietnam, ordered the invasion of Cambodia and Laos to distract some attention away from domestic discord.
Clinton, in the late 90s, faced with impeachment hearings and legal troubles over Watergate, inflated certain reports to give the impetus for bombing Iraq and for active intervention in the Balkans. Trying to take attention away from domestic troubles.
In 1916, Wilson ordered the US Army to capture Poncho Villa and invade Mexico. Possibly to take attention away from the calls for war or neutrality in Europe.
And now, Barack Obama is besieged on all sides. People on the left say he's not doing a good job, people on the right say he's a failure. AP Factcheck is calling him a bald-faced liar. He's got zero credibility.
And Mexico seems to be mere months from total collapse...
Primacy of Domestic Politics, anyone?