Dr. Monica Wehby greets supporters at the headquarters in Oregon City, Oregon after winning the Oregon Republican primary race for Senate on May. 20, 2014. Wehby, a pediatric neurosurgeon, has said she backs some portions of the Affordable Care Act, including the ban on discriminating against consumers on the basis of preexisting conditions and the provision allowing parents to keep their children on their plans up until age 26, according to spokesman Charlie Pearce. (Steve Dykes/AP)

Republican candidates have begun to retreat in recent weeks from their all-out assault on the Affordable Care Act in favor of a more piecemeal approach, suggesting they would preserve some aspects of the law while jettisoning others.

The changing tactics signal that the health-care law — while still unpopular with voters overall — may no longer be the lone rallying cry for Republicans seeking to defeat Democrats in this year’s midterm elections.

The moves also come as senior House Republicans have decided to postpone a floor vote on their own health-reform proposal, making it less likely that a GOP alternative will be on offer before the November elections, according to lawmakers familiar with the deliberations. The delay will give them more time to work on the bill and weigh the consequences of putting a detailed policy before the voters in the fall, lawmakers said.

On the campaign trail, some Republicans and their allies have started talking about the health-care law in more nuanced terms than they have in the past.

The U.S. Chamber of Commerce is running ads suggesting that many of its favored candidates will tweak Obamacare rather than scrap it. One spot says that Rep. Joseph J. Heck (R-Nev.) will fix the law, while another says Republican House contender Richard Tisei in Massachusetts will “work in a bipartisan manner to fix health care the right way.”

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The business group’s ads in Kentucky use almost identical language, declaring in separate spots that Sen. Mitch McConnell (R) and Rep. Garland “Andy” Barr (R) would work to “fix” the “Obamacare mess.”

In Oregon, GOP Senate candidate and pediatric neurosurgeon Monica Wehby backs the ban on discriminating against consumers on the basis of preexisting conditions and the provision allowing parents to keep their children on their plans until age 26, according to spokesman Charlie Pearce. While she opposes other aspects of the law and would like to replace it, Pearce said, she does not see that as realistic while “the president’s in office.”

GOP Senate candidate Terri Lynn Land in Michigan has called for the health-care law’s repeal. But on Friday, Land spokeswoman Heather Swift said the candidate applauds a move by Gov. Rick Snyder (R) to expand Medicaid coverage under the law.

Some Republicans are grappling with how to characterize their views. Scott Brown, a former senator from Massachusetts who now is running for a Senate seat in New Hampshire, continues to campaign against the law. But Brown also acknowledges keeping his 23-year-old daughter on his insurance plan, which would not be offered without the health-care law, and has declined to say whether he would endorse expansion of the Medicaid program in the state.

Will Hurd, a GOP House candidate running against Rep. Pete Gallego (D-Tex.) in the state’s only competitive congressional race, said this week in an interview that there are two “simple things” he would fix about the law. He would provide tax credits to individuals seeking care and allow people to buy plans being sold in other states.

In Minnesota, Republican House candidate Stewart Mills pledges in a campaign ad to “replace” the law rather than simply repealing it.

Elizabeth Wilner, a senior vice president at Kantar Media, wrote in a recent column for the Cook Political Report that after more than $400 million worth of ads opposing the law in recent months, “a shift already is underway” on the airwaves.

The law, which had a rocky rollout in the fall, managed to exceed its enrollment goals last month but still struggles to gain traction with voters. A Gallup poll released Thursday found that 51 percent of Americans disapprove of the Affordable Care Act, while 43 percent approve. But surveys consistently find that fewer than four in 10 want to repeal the law, while about six in 10 prefer making changes or improvements to the current framework.

“The sentiment toward the Affordable Care Act is still strongly negative, but people are saying, ‘don’t throw the baby out’ ” with the bath water, said Glen Bolger, a partner with the GOP polling firm Public Opinion Strategies.

Democrats such as Rep. Steve Israel (N.Y.), who chairs the Democratic Congressional Campaign Committee, said the latest shifts show that the GOP’s plan to repeatedly attack the Affordable Care Act has “backfired.”

“Now they’re promising fixes but won’t be specific,” Israel said in a statement. “That’s like a car dealer offering you a trade-in without telling you the car you’re getting in return.”

McConnell, who has vowed to rip up Obamacare “root and branch,” is under fire for saying his opposition to the law is “unconnected” to the fate of his state’s health insurance exchange, Kynect, suggesting the state could keep the system without the Affordable Care Act.

Kynect received $252 million in federal grants under the law, according to state officials, while the Medicaid expansion stemmed from a mandate that the program cover Americans living at 138 percent of the federal poverty line or less. Nearly 82,000 residents signed up for private insurance, and 331,000 were deemed eligible for Medicaid coverage.

In Washington, several chairmen of House committees told GOP leaders at a meeting last week that they would prefer to wait until next year to vote on a comprehensive health-care alternative, according to Republicans who spoke on the condition of anonymity to discuss internal deliberations.

House Majority Leader Eric Cantor (R-Va.) said deliberations will continue and a vote on a GOP plan remains a priority. Many GOP lawmakers are unsure whether the party should unveil their plans now or wait for a possible Senate takeover.

House Republicans had initially planned to test different health-care messages during the spring recess.

“The wave of the election is already within sight, and I believe we are going to do well,” said House Chief Deputy Whip Peter Roskam (R-Ill.). “I don’t think we need a replacement bill to win the election, but it is something that would be helpful in guiding our governing agenda for next year.”

A significant number of GOP Senate and House aspirants still back the idea of fully repealing the Affordable Care Act, including Senate candidates Tom Cotton (Ark.) and Thom Tillis (N.C.).

Only a handful of ads on behalf of Democratic congressional candidates attack Republicans for wanting to abolish the law. Minnesota Democrat Mike Obermueller has a commercial showing the dance party that would break out among insurers if his opponent, Rep. John Kline (R), were able to reverse it.

Most Democratic Senate incumbents have been more cautious, although all say they stand by the law they voted for 41 / 2 years ago. No vulnerable Senate Democratic incumbent has run an ad touting his or her vote in favor of the law, and Grimes made a point of saying last week, “If I had been in the Senate, it would have been a different law.”

Jahan Wilcox, spokesman for the Republican National Committee, wrote in an e-mail to reporters that Democrats will soon discover that the law remains a serious political liability.

“We are thrilled Democrats are set to embrace their job-killing healthcare law,” Wilcox wrote.

Ed O’Keefe contributed to this report.