PORTLAND — Local and regional Planned Parenthood officials say if the U.S. Supreme Court throws out buffer zones intended to keep anti-abortion protesters away from their clinics, similar protective areas aimed at safeguarding voters’ rights at the polls could be jeopardized as well.

The nation’s highest court is expected to hear oral arguments in the case of McCullen v. Coakley, in which a Massachusetts law establishing a 35-foot buffer zone around reproductive health care centers is being challenged as an infringement on protesters’ constitutional free-speech rights.

The case is expected to have a ripple effect wherever measures are being taken to keep anti-abortion demonstrators certain distances away from the clinics.

In Portland, where a 39-foot buffer zone was passed by the City Council in November, Planned Parenthood leaders are watching the Supreme Court case closely to see whether it affirms the legality of the local ordinance or opens the door to a legal challenge by protesters from the Pro-Life Missionaries of Maine.

An email sent to the missionary group and a phone call to one of its leaders were not immediately returned Wednesday.

“We’re paying close attention to the Supreme Court case,” said Nicole Clegg, spokeswoman for Planned Parenthood of Northern New England in Portland. “We’re certainly optimistic that the case will be resolved in our favor and the Portland buffer zone will not be impacted.”

Clegg echoed comments by Planned Parenthood colleagues from Massachusetts by saying Wednesday afternoon that in Maine’s largest city, the newly implemented buffer zone has “made a difference.”

While Planned Parenthood clients surveyed internally last winter and spring overwhelmingly said they felt “threatened and harassed” by the demonstrators — one woman told the council in November a protester pledged to “bound me at the knees and lower me into a lake of fire” — those same clients are feeling more comfortable now that the buffer zone is in place, Clegg said.

The 39-foot bubble effectively forces protesters — who had previously held weekly Friday and sometimes Saturday morning demonstrations along the stretch of sidewalk leading into the clinic’s 443 Congress St. door — across the street.

“Our patients have commented on the different experience they’re having entering our facility,” she said. “And yet it still allows people to express their First Amendment rights.”

Martha Walz, CEO of the Planned Parenthood League of Massachusetts and the former state legislator who sponsored that state’s buffer zone law now being challenged, said she and her organization “deeply value free speech and the right to privacy.”

Buffer zone advocates in Portland and Massachusetts have argued that, while demonstrators have a constitutionally protected right to assemble and protest, patients have a federally protected civil right to access health care without harassment.

In Portland, city councilors who voted unanimously to draw the line at 39 feet away from the clinic doors, said they felt they struck the proper balance in preserving the rights of both groups.

“Outside the buffer zones, protests can and do occur, so the law only regulates where people can stand, not what they can say,” Walz said during a Planned Parenthood conference call with reporters Wednesday morning. “It takes about seven seconds to walk from the edge of the buffer zone to our front door. That seven seconds of not being harassed on the way to the front door makes a huge difference. … [Previously], I remember one of the protesters just screaming at me, just inches away from my face, as I was in the facility doorway. It was scary.”

Teresa Roberts, a registered nursed at Planned Parenthood’s Greater Boston Health Center, added: “There’s a huge difference between four protesters standing 35 feet away and four protesters standing shoulder-to-shoulder in the doorway to our clinic.”

In addition to Massachusetts, Colorado and Montana have statewide abortion clinic buffer zone laws. Many municipalities across the country, including Portland and Burlington, Vt., have local ordinances that established such buffer zones.

Roger Evans, senior director of public policy law for the Planned Parenthood Federation of America, said the ramifications of a Supreme Court ruling against the buffer zone could be felt far outside the world of abortion clinics.

“Buffer zones to maintain order are not unique to our world,” Evans said during the Wednesday conference call. “There are buffer zones around polling places, there are even buffer zones in effect around the Supreme Court.”

The rules in place regulating activity around polling places aim to prevent voters from being bullied into casting votes a certain way. According to the National Association of Secretaries of State, a person may not attempt to influence a voter’s decision on public property within 250 feet of a polling place on Election Day in Maine.

In Maine, candidates and campaigners can stand outside the polls and interact verbally with voters, but only if they refrain from stating the name of the office they’re seeking and from requesting a vote outright.

Clegg said her organization is taking a “wait and see” approach in terms of how it will react to the Supreme Court’s eventual ruling.

“The Supreme Court could rule on the Massachusetts law in such a way that it doesn’t affect us in Portland,” she said. “We just don’t know.”