In 1970, Washington became the first -- and remains the only -- state in the country to legalize elective abortions by a popular vote.

A generation later, and 40 years removed from the landmark United States Supreme Court Roe v. Wade ruling that extended abortion access nationwide, Washington is once again poised to stand out.

With 21 states having adopted bans or severe restrictions on insurance companies from paying for abortions, Washington is alone in seriously considering legislation mandating the opposite.

The Reproductive Parity Act, as supporters call it, would require insurers in Washington state who cover maternity care -- which all insurers must do -- to also pay for abortions.

The bill passed the state House earlier this month by a vote of 53-43, though it faces an uncertain future in the Senate. A similar bill in the New York state Assembly has been introduced each session for over a decade but has never received a public hearing.

"This is a core value for Washingtonians," said Melanie Smith, a lobbyist for NARAL Pro-Choice Washington. "We should protect it while we still have it and not leave access to basic health care up to an insurance company."

The proximate cause of Washington state's measure is the federal Affordable Care Act. Thanks to language placed in it to assuage anti-abortion congressional Democrats, insurers selling their plans on the state exchanges taking effect next year will have to segregate the premiums they collect for abortion coverage.

In addition to that built-in disincentive to insuring abortion, the law also invites states to enact stricter rules of their own. Thus far, 16 states have followed suit, barring or restricting insurance companies on their exchanges from covering the procedure. Three of those states are joining the five that have barred or limited all insurers from covering abortions since the early 1980's.

Supporters of Washington state's proposed abortion insurance mandate are careful to stress that it wouldn't lead to a dramatic uptick in abortions or require carriers with a religious bent to cover the procedure. They also note that a pair of federal plans that will be sold on all 50 state exchanges will be barred from covering elective abortions.

"It's not expanding abortion coverage," said Democratic Rep. Eileen Cody of West Seattle, the bill's primary sponsor. "It's ensuring the rights of women to get what they're paying for now and to continue their freedom of choice."

Opponents counter that the measure would require businesses and individuals to pay for abortion coverage they'd rather not have.

"Washington state would be the only state in the country that would force employers to pay for abortion," said Peggy O'Ban, spokeswoman for Human Life of Washington.

If passed, she said, it would amount to "the first conscience coercion act in American history."

Its passage, however, is not assured.

Proponents of the measure say they have the votes they need in the state Senate, but it's not clear that Senate leaders will allow it to get to the floor. It is scheduled to receive a public hearing in the Senate Health Care Committee on April 1.

Ironically, the man bill supporters will likely blame if it fails to get a Senate vote counts himself as a proud backer of the measure.

Sen. Rodney Tom of Medina, a fiscal conservative and social moderate, and one other like-minded Democrat crossed party lines to caucus with Republicans in December, handing a one-vote majority to the GOP. Seizing power for the first time in nearly a decade, elated Senate Republicans reciprocated by installing Tom as Majority Leader.

Last month, Tom addressed about 250 advocates rallying for the measure's passage on the state Capitol steps.

"I'm down here making sure that my 17-year-old daughter has the kind of protections that we need in Washington state and that all of our kids have those same kinds of protections," Tom said to cheers.

Moments later, Gov. Jay Inslee, a Democrat and fellow bill supporter, delivered a not-so-subtle challenge to Tom's political will.

Washington state "deserves a vote in the state Senate on the Reproductive Parity Act," Inslee said. "We are going to insist that we are not going to let anybody close the door to democracy in this state."

Another irony: though the bill has proved to be among the most hotly contested of the session, its broader impact if passed may be less than sweeping.

For one thing, most abortions are paid for out-of-pocket. According to the Guttmacher Institute, only 12 percent of abortions nationwide are paid for by private insurers, with 20 percent footed by Medicaid.

For another, because most abortions cost less than a live birth -- the procedure typically runs about $500, though late-term abortions are far more expensive -- insurers may be disinclined to stop covering them.

At present, all major insurers in Washington state cover abortions, and Cody, the bill's sponsor, said she knows of no carrier with plans to change. Insurers new to Washington state on its exchange may be tempted to adopt different policies, she said.

No matter its immediate impact, said Elizabeth Nash, states issues manager with the Guttmacher Institute, the bill's passage would be a watershed event.

"It would be a model for other states to follow," she said.