The graph above is by the Congressional Budget Office, nominally nonpartisan but in practice now heavily influenced by the Republican Congress. The horizontal lines represent average revenues and spending as a function of GDP. The gap between the two represents the long-term deficit.
In 1968, due to Vietnam spending by Lyndon Johnson, spending reached 21% of GDP.
At the time, that was regarded as scandalous, big government out of control. In addition, revenues were down at about 18% of GDP, leading Johnson to implement the infamous "unified budget," in which Social Security revenues masked the deficit.
Under Nixon-Ford, revenues fell (due to recession), yet outlays rose and rose. Under Carter, outlays fell and revenue rose. Under Reagan, outlays exploded and revenue fell. Under Clinton, outlays dropped and revenues rose. Under Bush, revenues collapsed and outlays rose, creating massive deficits.
This explains why Republicans have won the elections they have: they have spent and spent, while leaving tax collection to the Democrats.
What the graph doesn't explain is how Republicans got a reputation for fiscal conservatism. They are grasshoppers, playing away the summer, while our nation's winter approaches.