Nixon pushes a modified version of his negative income tax (aka guaranteed annual income) that gathers support via liberals—by giving everyone a certain amount of money every year—and via conservatives by means-testing social programs, not indexing them to inflation, and eliminating welfare.
In the Senate, under pressure from multiple sides, and with Nixon's popularity still high Ted Kennedy and the other liberal hold-outs agree to back Nixon's national healthcare plan.
(POD: Nixon shows somewhat more interest in domestic affairs.)
OTL:
Nixon's negative income tax fails in Congress under conservative pressure because it fails to do anything about the social programs it's designed to replace.
Nixon's national healthcare plan is rejected by liberal Democrats who believe they will elect a fellow Democrat in '76 (true) and that they will then get single payer Canadian style healthcare (false).