Texas and Illinois are the poster children for what’s wrong with congressional redistricting. In Illinois, Democrats did a number on Republicans; in Texas, Republicans are doing it to Democrats.

And both did it in part by diluting the voting power of their growing Hispanic populations, especially in major metropolitan areas like Dallas, Houston and Chicago.

That could run them afoul of the 1965 Voting Rights Act, designed to protect the voting influence of minorities. It could provide a major judicial test of whether the law initially passed to protect African-Americans may now bolster Hispanics’ increasing political clout.

On the surface, the numbers suggest Illinois Democrats altered the political balance more than Texas Republicans did. The Illinois plan, already enacted, could transform its U.S. House delegation from 11-8 Republican to a 12-6 or even 13-5 Democratic advantage.

But even without a process controlled by a Democratic legislature and governor, some Illinois Republicans were living on borrowed time. Eight of the 11 GOP House members represent districts President Barack Obama carried in 2008, including five freshmen elected in 2010. While some new districts seem competitive, Obama carried them all.

The plan retains Illinois’ three black majority and one Hispanic majority districts. But its overall population now includes more Hispanics than blacks, and Illinois Republicans are threatening a legal fight for a second Hispanic district, primarily hoping to win some districts that would lose Latino voters.

In Texas, Democrats say the latest plan being considered by the legislature’s Republicans would change the current GOP 23-9 majority to 26-10. Beyond the numbers, it raises major issues because of its projected impact on the state’s burgeoning Hispanic population.

It would protect Republican seats held by freshmen Reps. Blake Farenthold of Corpus Christi and Francisco Canseco of San Antonio by making their districts less Hispanic.

And while it creates two new Hispanic-majority districts in the Austin-San Antonio and Gulf Coast areas, Democrats make a good case that those merely replace Farenthold’s current Hispanic-majority district, represented until this year by Democrat Solomon Ortiz, and the Austin-area seat of liberal Democratic Rep. Lloyd Doggett, where Hispanics are a significant minority.

It also limits the Latino community’s impact in the Dallas and Houston areas by dividing much of its population growth into safely Republican majority-white districts.

Instead, it creates four new districts likely to elect Republicans: in the Corpus Christi area, the Houston-Beaumont area, west of Fort Worth (where one potential aspirant is Railroad Commissioner Michael Williams, a black GOP conservative), and in the rural areas between Austin and Fort Worth. (To have any chance of survival, Doggett would have to run in the new Hispanic district.)

The result reduces from 11 to 10 the number of districts in which minority voters could control the outcome, says Matt Angle, a longtime Democratic congressional aide and redistricting strategist.

“They take a state that picks up four districts because of minority growth and reduce the number of districts in which minorities have the opportunity to elect a candidate of their choice,” he said.

Though Republicans insist their plan is fair, it’s certainly headed for the courts. Unless significantly changed, it would extend the job former House Majority Leader Tom DeLay started a decade ago to maximize GOP strength and eliminate white Democrats. Besides Doggett, the only other remaining white Democrat, Rep. Gene Green of Houston, represents a heavily Hispanic district.

Hispanic leaders, mostly Democrats, are rightly irate. Its maximum projected total of eight Hispanic members — including two Republicans whose districts have white voting majorities would give Latinos just 22 percent of the congressional membership, even though the 2010 census reported Texas is now 38 percent Hispanic.

Interestingly, one aspect of the Republican plan mirrors a 2003 GOP move the U.S. Supreme Court rejected.

It would preserve Canseco’s seat by reducing his district’s Hispanic population, just as the 2003 plan did in seeking to save GOP Rep. Henry Bonilla. When the Supreme Court added more Hispanics, Bonilla lost.

It’s hardly new for one party to pad its numbers when it controls redistricting. The factor that may make the Illinois and Texas plans important legal tests is that neither reflects the country’s most significant demographic change, the growth of its Hispanic population.