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.