Election variables:

Year = election year (1916 to 1996).

Votes = percent of the two-party vote received by the incumbent party candidate.

Incumbent = 1 if the candidate is the incumbent, = 0 otherwise.

Growth = the growth rate, in percent, of real GDP over the three quarters prior 
	 to the election.

Inflation = the inflation rate, in percent, over the 15 quarters prior to the election.