WASHINGTON (AP) – The Obama administration and civil rights groups are defending a key section of the landmark voting rights law at the Supreme Court by pointing reformed state, county and local governments to an escape hatch from the law's strictest provision.

The Voting Rights Act effectively attacked persistent discrimination at the polls by keeping close watch, when it comes to holding elections, on those places with a history of preventing minorities from voting. Any changes, from moving a polling place to redrawing electoral districts, can't take effect without approval from the Justice Department or federal judges in Washington.

But the Voting Rights Act allows governments that have changed their ways to get out from under this humbling need to get permission through a “bailout provision.” Nearly 250 counties and local jurisdictions have done so; thousands more could be eligible based on the absence of recent discriminatory efforts in voting.

The viability of the bailout option could play an outsized role in the Supreme Court's consideration of the voting rights law's prior approval provision, although four years ago, conservative Justice Clarence Thomas said the prospect of bailing out had been “no more than a mirage.”

The court will hear arguments Wednesday in the case, which is among the term's most important, in a challenge from Shelby County, Ala.

Opponents of the law say they no longer should be forced to live under oversight from Washington because the country has made enormous racial progress, demonstrated most recently by the re-election of President Barack Obama. They object in particular to the 40-year-old formula by which some jurisdictions, most in the Deep South, are swept under the law and others remain outside it.

The administration and its allies acknowledge that there has been progress. But they say minority voters still need the protection the law affords from efforts to reduce their influence at the polls. Last year, federal judges in two separate cases blocked Texas from putting in place a voter identification law and congressional redistricting plan because they discriminated against black and Hispanic residents.

Obama himself talked about the case in a radio interview last week. He told SiriusXM host Joe Madison that if the law were stripped of its advance approval provision, “it would be hard for us to catch those things up front to make sure that elections are done in an equitable way.”

Also, the law's defenders say places that have changed their ways can win release from having to get Washington's blessing for election changes. Governments seeking to exit have to show that they and the smaller jurisdictions within their borders have had a clean record, no evidence of discrimination in voting, for the past 10 years.

Shelby County has never asked to be freed from the law, but would seem to be ineligible because one city in the county, Calera, defied the voting rights law and prompted intervention by the Bush Justice Department.

Yet places with a long, well-known history of discrimination probably could find their way out from under federal monitoring, according to a prominent voting rights lawyer who used to work for the Justice Department.

“Birmingham, Ala., where they used to use fire hoses on people, may well be eligible to bail out,” said the lawyer, Gerry Hebert. Birmingham officials said they've never considered asking.

The Supreme Court made clear its skepticism about the ongoing need for the law when it heard a similar case in 2009. “Past success alone, however, is not adequate justification to retain the preclearance requirements,” Chief Justice John Roberts said for the court. That ruling sidestepped the constitutional issue and instead expanded the ability of states, counties and local governments to exit the advance approval process.

At that point, so few governments had tried to free themselves from the advance approval requirement that, in 2009, Thomas said the “promise of a bailout opportunity has, in the great majority of cases, turned out to be no more than a mirage.”

At the time, Thomas said, only a handful of the 12,000 state, county and local governments covered by the law had successfully bailed out.

The overall numbers remain low, but the Obama administration argues that “the rate of successful bailouts has rapidly increased” since the high court last took up the Voting Rights Act nearly four years ago.

In the past 12 months, 110 local governments have been freed from the requirement to show in advance that their proposed election changes are not discriminatory. Places that have won their release from coverage include Prince William County, Va., with more than 400,000 residents, and Merced County, Calif., and its 84 municipalities.

Shelby County says that even with the recent jump in bailouts, “only a tiny percentage” of governments have found their way out of oversight from Washington.

The advance approval was adopted in the Voting Rights Act in 1965 to give federal officials a potent tool to defeat persistent efforts to keep blacks from voting.

The provision was a huge success, and Congress periodically has renewed it over the years. The most recent time was in 2006, when a Republican-led Congress overwhelmingly approved and President George W. Bush signed a 25-year extension.

The requirement currently applies to the states of Alabama, Alaska, Arizona, Georgia, Louisiana, Mississippi, South Carolina, Texas and Virginia. It also covers certain counties in California, Florida, New York, North Carolina and South Dakota, and some local jurisdictions in Michigan and New Hampshire. Coverage has been triggered by past discrimination not only against blacks, but also against American Indians, Asian-Americans, Alaskan Natives and Hispanics.

The 10 covered towns in New Hampshire are poised to become the next places to win their release from the law. An agreement between the Justice Department and the state is awaiting approval from a federal court in Washington.

Critics of the law contend the Justice Department is highlighting the escape hatch and agreeing to allow places such as the New Hampshire towns to exit to try to make the entire law look more palatable to the court.

Alaska Attorney General Michael Geraghty says in his court filing in support of Shelby County that the Justice Department “commonly agrees to bailouts for jurisdictions that are not legally entitled to receive them.”

But supporters of the law argue in response that the federal government's willingness to agree to free places from the need to get permission shows that the voting rights act is flexible and helps focus attention on potentially discriminatory voting schemes.