I had not heard the term, but here's how W'pedia describes it, quite fifferently that
4bonhoffer, BTW,
https://en.wikipedia.org/wiki/Jude_Wanniski#The_Two_Santa_Claus_Theory :
The Two Santa Claus Theory
The Two Santa Claus Theory is a political theory and strategy published by Wanniski in 1976, which he promoted within the United States Republican Party. The theory states that in democratic elections, if members of the rival Democratic Party appeal to voters by proposing programs to help people, then the Republicans cannot gain broader appeal by proposing less spending. The first "Santa Claus" of the theory title refers to the Democrats who promise programs to help the disadvantaged. The "Two Santa Claus Theory" recommends that the Republicans must assume the role of a second Santa Claus by not arguing to cut spending but offering the option of cutting taxes.
According to Wanniski, the theory is simple. In 1976, he wrote that the Two-Santa Claus Theory suggests that "the Republicans should concentrate on tax-rate reduction. As they succeed in expanding incentives to produce, they will move the economy back to full employment and thereby reduce social pressures for public spending. Just as an increase in Government spending inevitably means taxes must be raised, a cut in tax rates—by expanding the private sector—will diminish the relative size of the public sector." Wanniski suggested this position, as left-liberal observer Thom Hartmann has clarified, so that the Democrats would "have to be anti-Santas by raising taxes, or anti-Santas by cutting spending. Either one would lose them elections."
I've also never heard of Jude Wanniski.
His "Theory", carried out, would benefit the economy two ways: government takes less $$ out of the economy
by force; people invest less conservatively - = safer
low-tax investments - and instead invest in businesses, which are higher risk, higher profit, and, paradoxically, result in increased government revenue. Arthur Laffer, at least, apparently predicted that paradoxic outcome.