For years, Republicans savaged Democrats for supporting the Affordable Care Act, branding the law — with some rhetorical license — as a government takeover of health care.

Now, cast out of power in Washington and most state capitals, Democrats and activist leaders seeking political redemption have embraced an unlikely-seeming cause: an actual government takeover of health care.

At rallies and in town hall meetings, and in a collection of blue-state legislatures, liberal Democrats have pressed lawmakers, with growing impatience, to support the creation of a single-payer system, in which the state or federal government would supplant private health insurance with a program of public coverage. And in California on Thursday, the Democrat-controlled State Senate approved a preliminary plan for enacting single-payer system, the first serious attempt to do so there since then-Gov. Arnold Schwarzenegger, a Republican, vetoed legislation in 2006 and 2008.

With Republicans in full control of the federal government, there is no prospect that Democrats can put in place a policy of government-guaranteed medicine on the national level in the near future. And fiscal and logistical obstacles may be insurmountable even in solidly liberal states like California and New York.