When Alabama Republicans moved thousands of black voters into new legislative districts, did they do so because of the way blacks vote or because of their race itself?

That's the question the U.S. Supreme Court will have to decide. The Court on Wednesday will hear oral arguments in cases brought by Democrats and black legislators challenging districts drawn by Republicans after they took control of the legislature in the 2010 elections.

It's the first racial gerrymandering case the Court has heard in 13 years. It could have an impact on congressional and legislative maps across the country.

African Americans overwhelmingly vote Democratic, so Republican legislators have long sought to pack as many blacks as possible into majority-minority districts, leaving neighboring districts more likely to vote Republican.

"Gerrymandering does bleach black voters from surrounding districts, leaving them much whiter and, in the South, making them much more susceptible to electing Republican candidates," said Abigail Thernstrom, a former vice chair of the U.S. Commission on Civil Rights. "In my first book, I said that Republicans were laughing all the way to the political bank with these districts."

If Alabama Republicans were strictly seeking to retain partisan advantage, that's something courts have always blessed in redistricting. Andrew Brasher, the state's solicitor general, said that helping white Democrats win outside of majority-black districts was most assuredly not a GOP priority. "What possible reason would the legislature have to do that?" he told USA Today.

But since the 1990s, the Supreme Court has held that the use of race as the "predominant factor" in redistricting is unconstitutional. Courts have cast a skeptical eye on racially-driven maps that ignore traditional redistricting priorities, such as compactness.  

Last month, a federal court ruled that Virginia's congressional map violated the Constitution by concentrating African Americans into a single congressional district, diluting their influence elsewhere and violating the Equal Protection Clause of the 14th Amendment.

"Republicans had this strategy of creating very safe Democratic maps packed with minorities across the South, and not just the South," said Michael McDonald, a University of Florida political scientist who served as an expert witness in the Virginia case.

Alabama is arguing that it simply sought to preserve the proportion of African Americans living in the majority-minority districts as they'd been drawn a decade ago. Democrats are just mad that they've lost their traditional hold on power, Republicans say.

"This case is not about race or even civil rights issues, generally," lawyers for the top GOP legislative leaders wrote in a brief. "Rather, it is about the Alabama Democratic Party's loss of 136 years of uninterrupted legislative power."

The Democrats and black legislators who filed suit said the legislative maps have had the effect of quarantining African American representation, limiting black voices to a handful of majority-minority districts. In one notable instance, Republicans added nearly 15,000 African Americans and just 36 whites to one state Senate district that was already majority-minority but is now 75 percent black.

"What the plaintiffs are alleging is that Alabama was ham-handed and blunt in its use of race, that the Voting Rights Act requires a nuanced examination of the political facts on the ground," said Justin Levitt, a law professor at Loyola Law School in Los Angeles. "Instead, Alabama chose certain demographic targets it had the last time, without ever looking at whether facts have changed."

Levitt contends that the case, while it may be about redistricting on its face, is really about the broader question of when and how government agencies should consider race. In recent cases on other issues such as education, the Court has permitted "nuanced" use of race, he said, but has been dubious about letting race trump all other concerns.

He and McDonald are skeptical that the Court will use the Alabama cases to overturn broad sections of the Voting Rights Act. Thernstrom said the justices are impatient and "fatigued" with racially-driving districting, but she hesitated to predict an outcome in this instance.

The Court may indeed decide to use the case as a vehicle to encourage more challenges to the Voting Rights Act, suggests Michael Li, a redistricting expert at New York University's Brennan Center for Justice. Or, it could simply uphold the decision from a lower court, giving its blessing to majority-minority districts, even if minority politicians themselves don't like them.

"If the Court says this map is based on politics, not race, then Republicans in the South would have the ability to substantially disadvantage minority voters," Li said. "It would be a free-for-all, a sort of Wild West setting."

The Court agreed to hear another redistricting case, involving Arizona's use of commissions to draw maps, later in this term.