While the potential impact remains uncertain, both Democratic and Republican leaders agree that the ruling could solidify the Democrats' tight grip on California's 53-member House delegation, the largest of any state.
The issue stems from a lawsuit filed by Arizona's Republican-led Legislature arguing that the Constitution gives state legislatures the exclusive responsibility for drawing congressional district boundaries. Arizona and California voters have passed measures removing that authority from lawmakers and handing it over to independent citizen commissions.
But the court's conservative justices appeared skeptical of the constitutionality of such commissions during arguments Monday. If the Supreme Court strikes down the citizen panels, the task of remapping California's congressional districts would return to the Democratic-controlled Legislature, albeit with the blessing of fellow Democrat Gov. Jerry Brown, who wields veto power.
Former Republican Gov. Pete Wilson said Tuesday that Democrats in the past used that power to gerrymander district lines to help expand their numbers, protect entrenched incumbents and undercut the GOP.
"It was an utterly corrupt situation, one in which the inherent, unescapable conflict of interest was egregious,'' said Wilson, who joined with former Republican Govs.
Wilson, using his veto power, waged a bitter battle with the Legislature's Democratic leadership in the early 1990s that put redistricting in the hands of the California Supreme Court.
John Burton, chairman of the California Democratic Party, cautioned that it's too early to speculate about how the pending court decision could affect the California Citizens Redistricting Commission.
Still, he said, if the authority over drawing congressional boundaries returns to the California Legislature, "that wouldn't be bad" for Democrats.
"The state of California is more Democratic, by [voter] registration and also by people whose politics are in concert with the Democrats," Burton said.
Michael Wagaman, a Democratic consultant on redistricting, said he did not expect legislative Democrats to drastically alter district lines even if California's independent panel is declared unconstitutional. In part, that's because the current congressional map is treating them well.
"The Republicans are at the lowest percentage of the congressional delegation since the New Deal," Wagaman said. "Anybody expecting a 'Girls Gone Wild' scenario from California Democrats is going to be sorely disappointed."
California voters approved the Voters First Act in 2008 to create the redistricting commission for legislative seats. Two years later, voters approved a measure to extend its authority to congressional districts.
The legal challenge in front of the Supreme Court is expected to affect only the panel's authority to draw congressional districts, said Angelo Ancheta, a Santa Clara University law professor and member of the redistricting commission. Even if that authority was declared unconstitutional, the panel still would have the authority to draw legislative district boundaries, he said.
Ancheta said the independent panel's goal was to ensure, with input from the public, that political districts represented "communities of interest" that could be bonded by geography, economic interest or other factors.
What was eliminated was the old practice of contorting districts to protect incumbents, a process often guided by pooling greater numbers of Democrats or Republicans into a district — a process known as gerrymandering.
"Whoever has the power in the Legislature is going to want to keep that power," he said.
Every 10 years, after the U.S. census, district boundaries must be redrawn to ensure that districts have equal populations. If California's citizen panel is declared unconstitutional, new congressional district boundaries could possibly be redrawn by the 2016 election.
California Republicans were bracing themselves for the Democrats to take full advantage of the redistricting pen. State party Chairman Jim Brulte said it was unlikely that Republicans could benefit should the Legislature redraw district lines.
"[Perhaps] if the liberals who currently control the Legislature suddenly have an epiphany, but I don't bank on that," Brulte said. "Redistricting is the most partisan activity legislators can engage in. All you have to do is look at what happens all across the country when one party controls the entire process."
Demographics also will be a major factor.
State GOP General Counsel Charles Bell said one bloc that may look to flex muscle is the Latino Democrats, whose growing strength in state politics was not fully reflected in the 2011 map drawn by the independent panel.
And Assemblyman Sebastian Ridley-Thomas (D-Los Angeles), a member of the Legislative Black Caucus, said any new lines drawn should follow "the spirit and the letter of the most inclusive form of the Voting Rights Act," despite the Supreme Court's invalidation of a major section of that law.
Ridley-Thomas, who chairs the Assembly elections and redistricting panel, said that law is "the reason we have the ethnic diversity of the legislative and congressional delegations that we do in California."