WASHINGTON (AP) — Their Senate majority in peril, anxious Democrats have seized the Supreme Court decision that some companies need not provide birth control to women as fresh evidence of the GOP's "war on women" — an argument they hope will energize female voters who could decide the balance of power on Capitol Hill.

Republicans aggressively cheered the high court's decision, but GOP leaders concede that their party must tread carefully. Even before Monday's decision was announced, GOP operatives coached their candidates to cast the ruling as a victory for religious freedom and further evidence that the country's health care law is deeply flawed.

"Republicans have to be careful about not appearing as though they're anti-contraception. This is a constitutional issue," said Katie Packer Gage, a GOP strategist whose firm advises Republicans on navigating women's issues. "We have to be very, very cautious as a party."

The GOP for years has tried to make inroads with two groups that tend to favor Democrats: women and younger voters. As popular as the court's decision will be with the Republican base, it's likely to be just as unpopular this election year and into 2016 with those who depend on insurance to pay for birth control — a group that includes women and younger voters.

"The thought of your boss telling you what kind of birth control you can and can't get is offensive and it certainly is motivating to women to vote," said Cecile Richards, president of Planned Parenthood Action Fund, which plans to spend several million dollars this year to campaign for Senate candidates.

The Supreme Court ruled 5-4 that some companies can hold religious objections allowing them to opt out of health law's birth control coverage requirement. While the ruling does not address the heart of the Affordable Care Act, it's a setback for Democrats and amplifies a longstanding argument from conservatives that the law they call "Obamacare" intrudes on religious liberties as part of a larger government overreach.

But Democrats in competitive congressional races are going on the offensive. They're using the ruling to shine a spotlight on their Republican opponents' record on reproductive rights — a push that dovetails with a strategy already aimed at mobilizing female voters on issues such as raising the minimum wage and supporting pay equity for women.

In North Carolina, incumbent Democratic Sen. Kay Hagan declared on Twitter that health care should be decided between a woman and her doctor — "not her boss." She and her allies are working to draw attention to her opponent, Republican state House Speaker Thom Tillis, and his efforts to restrict access to abortions.

It's a similar story in New Hampshire, where Democratic Sen. Jeanne Shaheen released an online petition Tuesday highlighting her Republican opponent, former Sen. Scott Brown, and his previous support for legislation that would have allowed any employer with moral objections to opt out of the birth control coverage requirement.

In Colorado, Democratic Sen. Mark Udall's first TV ad noted Republican Rep. Cory Gardner's past sponsorship of a bill to outlaw abortions in cases of rape and incest and support for an effort to grant an embryo the same legal rights as a person, which could have outlawed some types of birth control and all abortions. Gardner now says he opposes the "personhood" measure.

In Iowa, Democrats have signaled plans to highlight Republican Joni Ernst's support of a personhood amendment to the state's constitution. And in Montana, Democratic Sen. John Walsh aired an ad in May criticizing Republican Rep. Steve Daines' support of legislation to restrict access to abortions and quickly pounced on the Supreme Court ruling, saying it would "infringe upon the right to make private health choices."

It won't be clear until November whether women will respond to such appeals.

Fewer young women typically vote in midterm elections compared with presidential years. And they are particularly disengaged from this year's races in which Republicans need to pick up six seats to claim the Senate majority: 63 percent of women under age 30 in an AP-GfK poll conducted before the ruling reported they "don't care very much" which party wins control of Congress. Just 21 percent said they were certain to vote in November.

GOP leaders privately fear that one of their candidates will make a high-profile gaffe that could be used against all Republicans in the coming months. The party is still recovering from a series of insensitive comments made by GOP candidates in the 2012 election, including Missouri U.S. Senate candidate Todd Akin, whose campaign crumbled after he said women's bodies were able to avoid pregnancy in cases of "legitimate rape."

Reinforcing its decision of Monday, the high court on Tuesday left in place lower court rulings in favor of businesses that object to covering all methods of government-approved contraception.

The justices' action Tuesday was a strong indication that the earlier decision extending religious rights to closely held corporations applies broadly to the contraceptive coverage requirement in the health care law, not just the four pregnancy prevention methods and devices that the court considered in its ruling. Tuesday's orders apply to companies owned by Catholics who oppose all contraception. Their cases were awaiting action pending resolution of the Hobby Lobby case.

Polls suggest that most people — and a larger majority of women — think for-profit companies should be required to cover the cost of birth control. A Gallup survey conducted in May found that 90 percent of Americans, including 88 percent of Republicans, see the use of birth control as morally acceptable.

"The Democrat playbook this cycle is to run their disingenuous war on women campaign across the country," said Andrea Bozek, a spokesman for the House Republican campaign arm. "This time we'll be ready."

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Peoples reported from Boston. Associated Press writer Ricardo Alonso-Zaldivar and AP Director of Polling Jennifer Agiesta contributed to this report.