WASHINGTON - Forty years after the Supreme Court's Roe vs. Wade decision struck down laws forbidding abortions, support for a legal right to end a pregnancy has grown, according to polls released this week.

The shift has come largely from increased support for legal abortion among Latinos and blacks, according to a new NBJ/Wall Street Journal survey. The survey for the first time found a majority of American supporting legal abortion in all or most cases.

The shift among blacks and Latinos could indicate that both population groups, which have strongly supported the Democratic Party in recent years, have begun taking on the party's views on social issues.

The survey showed 31 percent of Americans saying abortions should always be legal and another 23 percent saying they should be "legal most of the time." The combined 54 percent support for legal abortion in most cases has moved upward from 44 percent a decade ago and 49 percent five years ago.

On the other side, 9 percent said abortions should be illegal without exceptions and 35 percent said they should be illegal but with some exceptions.

By 70 to 24 percent, those surveyed said they would oppose overturning the Supreme Court's abortion decision, with 57 percent saying they "feel strongly" that it should not be overturned. Five years ago, 65 percent said they opposed overturning the decision.

The shifts in public opinion might not appear huge, but they "are profound changes," Republican pollster Bill McInturff, whose firm conducted the survey with Democratic pollster Peter Hart, told NBC.

Although a majority support abortion rights, those in opposition more often consider the issue a top priority, according to a separate survey by the Pew Research Center.

According to the Pew survey, more than twice as many people support keeping Roe vs. Wade in place as want it overturned. Among those who want it overturned, 38 percent said they consider the issue "critical." Another 36 percent see abortion as one of many important issues facing the country and 25 percent see the issue as not that important.

Among the majority who favor keeping Roe vs. Wade in place, only 9 percent see the issue as critical, 22 percent see abortion as one of many important issues and 68 percent see it as not that important.

Political strategists say that voters who support abortion rights often put a low priority on the issue because, after 40 years, they take legalized abortion for granted.

A large percentage of Americans don't recognize the name Roe vs. Wade. Asked about the case by name, 41 percent in the NBC/Wall Street Journal survey said they had no opinion and 37 percent in the Pew survey could not correctly identify what the case was about.

Those surveyed had clear views when the ruling was identified to them as the one that established a constitutional right to abortions. Older Americans were significantly more likely than younger ones to identify the case correctly, Pew found.