In January, with much preening, House Democrats embraced "paygo," the pay-as-you-go rule that any tax cut must be "paid for" by compensatory tax increases or revenue cuts. In December, Democrats abandoned it because of the alternative minimum tax.
The AMT was enacted in 1969 as an indignation gesture aimed at fewer than 200 rich people who managed, legally, to owe no taxes. But the enactors neglected to index the AMT against inflation, so this year it would have been a $50 billion bite out of 23 million taxpayers. The House voted to repeal it and pay for repeal with a $50 billion tax increase. Senate Republicans argued that no Congress ever intended the AMT to collect, or ever will allow it to collect, such large sums from such a large number of Americans. Therefore, paygo would siphon $50 billion to compensate for a fictitious $50 billion. The Senate voted 88-5 to not collect the AMT this year, the House acquiesced and paygo evaporated.