WASHINGTON — Congressional efforts to repeal the Affordable Care Act sprang back to life on Monday as Senate Republicans pushed for a showdown vote on new legislation that would do away with many of the health law’s requirements and bundle its funding into giant block grants to the states.

The Republican leaders of the latest repeal effort, Senators Lindsey Graham of South Carolina and Bill Cassidy of Louisiana, said their effort — considered all but impossible earlier this month — was gaining momentum. The seven-year drive to repeal President Barack Obama’s signature domestic achievement appeared to collapse in July when it fell one vote short in the Senate.

And the same three Republicans who opposed it then — John McCain of Arizona, Susan Collins of Maine and Lisa Murkowski of Alaska — have yet to commit to voting for the latest repeal bill.

But the last-ditch repeal pitch received a jolt of energy on Monday when Gov. Doug Ducey of Arizona, a Republican, strongly endorsed it, putting pressure on Mr. McCain, who already faced the prospect of having to vote against his best friend in the Senate, Mr. Graham. Mr. Ducey had been a skeptic of earlier bills to repeal and replace the health law.