Bruce Bartlett discusses the Two Santas theory, which started Republicans down the supply side path and led them to the party of tax cuts for every social problem:
The essence of the Wanniski argument was that each political party needed to be a different sort of Santa Claus. The Democrats were the spending Santa Claus, promising more government benefits. The Republicans should be the tax-cut Santa Claus, he said.
... Republicans didn’t immediately embrace the two-Santa theory, but began to after Ronald Reagan’s victory in 1980, when he ran mainly in favor of a big tax cut, with far less emphasis on deficit reduction. In office, Reagan pushed for domestic spending cuts but also sharply raised spending for favored programs such as the military.
Although the budget deficit rose to 6 percent of gross domestic product in 1983 from 2.7 percent in 1980, Reagan easily won re-election in 1984. This further convinced Republicans that the deficit was a losing issue and only tax cuts mattered for political success.
The final straw was George H.W. Bush’s support for a tax increase in 1990 to reduce the deficit, which many Republicans say sealed his defeat in 1992 by Bill Clinton.
Since then, fealty to tax cuts and lip service to deficits has become Republican dogma.Norquist picked up the idea and ran with it, though apparently "thought of the same idea himself when he was in the seventh grade." If you haven't yet seen Samantha Bee's interview of Norquist and her exploration of his other grade school epiphany, the two-part pledge that has become the tax policy equivalent of an American flag lapel pin for Republican lawmakers, it's a must-see.