The Supreme Court today upheld the basic outlines of a Republican Congressional redistricting plan in Texas, refusing to toss out a sharply contested political map engineered by the former House majority leader, Tom DeLay.

The court handed a smaller victory to the Democratic plaintiffs in the case, ruling that one Congressional district in southwestern Texas had been drawn in a way that violated the rights of Hispanic voters there.

But the court rejected the larger premise — that Texas Republicans had unconstitutionally reorganized the political map to solidify their majority in Congress. The decision means that Texas will be required to adjust some boundaries.

The court upheld the state's ability to break with the tradition of redrawing Congressional districts only right after the official federal census every 10 years, potentially opening the door for legislatures in other states to rewrite their own Congressional maps at will throughout the decade, or when a new party takes over a state capital.

The outcome was something of a vindication for Mr. DeLay, who had been attacked by Democrats for organizing what they called an illegal power grab in his home state at the height of his service as majority leader. Republicans won five new Congressional seats in Texas in 2004 after the lines were redrawn, helping them retain control of the House.

"We reject the statewide challenge to Texas redistricting as an unconstitutional political gerrymander," Justice Anthony Kennedy wrote in the majority opinion.

The Democrats claimed unpersuasively, Justice Kennedy wrote, that because the Republican redistricting had been driven entirely by political motivations and was not tied to new Census results, it violated equal protection laws. The plaintiffs, he wrote, "had not given shape to a reliable standard for identifying unconstitutional political gerrymanders."

Still, the court found that the 23rd district, the seat held by Representative Henry Bonilla, a Republican, had been improperly redrawn to exclude an increasingly active Latino voting population. Creating a new district, the 25th, to address the imbalance was not sufficient, the court found.

The complex ruling included six separate opinions, and only Justice Anthony M. Kennedy joined both parts of the decision.

In his majority opinion, Justice Kennedy wrote that the Republican-controlled legislature "took away the Latinos' opportunity because Latinos were about to exercise it. This bears the mark of intentional discrimination that could give rise to an equal protection violation."

Another district in Dallas, the seat formerly held by Representative Martin Frost, a Democrat, was upheld. The Democratic plaintiffs in the case had claimed that African-American voters were disenfranchised by the new boundaries.

It was not immediately clear whether the district lines could be redrawn in time for the Congressional elections in November or whether any change to the districts would give Democrats a chance at picking up a seat there.

Robert Richie, the executive director of the Center for Voting and Democracy, a Washington based group that promotes competitive elections, said today that he hoped the Court's decision that mid-decade redistrictings were permitted would lead to an effort on Capitol Hill to set standards for the drawing of Congressional district lines.

"If there's no limits, it really opens the door to the partisan dynamic just getting worse and worse," said Mr. Richie. On the other hand, there are certainly situations in which drawing a new map in mid-decade makes sense, he said.

And overall, it would be better if the matter were debated and handled by elected officials, since asking judges to decide how much partisanship is too much will always be "messy," he said. "We should be looking at a political process solution."

The effort by Republicans to boost their representation in Congress began in 2000, when the state picked up two Congressional seats in the new census. The Republicans controlled the State Senate at the time, but the Democrats held onto control of the House, and the Legislature deadlocked over the question of drawing new district lines.

Instead, the job was handed to a federal court, which in 2001 produced a new map that was based in large part on the one adopted by a Democratic-controlled Legislature in 1991.

Republicans complained that the court's map ignored their political gains over the last decade, and Representative DeLay led an effort to take control of the House in the 2002 elections, in large measure to be able to take control of the redistricting process and force through a map more to his liking.

When Republicans took over the House in 2003 and announced their plans for a new round of redistricting, they said they were simply reclaiming a legislative prerogative that had been handed to the courts only because of the stalemate. Democrats complained that it was a breach of the tradition of redistricting only once a decade, using new census data.

They vowed to block what they called a naked power grab, but their only weapon in the face of Republican majorities was their ability to prevent the Senate from reaching a quorum, and twice they fled across state lines as a group to thwart attempts to bring the plan to a vote.

But that strategy collapsed in September, when Senator John Whitmire of Houston abandoned the Democrats who had holed up in New Mexico since late July. In October the Senate adopted the Republican plan by a 19-to-12 vote, with two Republicans joining all the voting Democrats in opposition.

Besides their objections to the mid-decade redrawing, Democrats complained that several of the new districts violated the Voting Rights Act by diluting minority influence.

Last December, Attorney General Alberto R. Gonzales acknowledged that the professional staff of the Justice Department's Civil Rights Division had also considered the plan to be in violation of the act.

In a memorandum, the six lawyers and two analysts in the voting rights section unanimously concluded that "the proposed plan reduces the level of minority voting strength." They were overruled by the top officials in the department.

While the court's decision today ends the redistricting, its consequences live on in other ways, including the indictment of Mr. DeLay on state campaign finance charges last year.

Mr. DeLay was charged with illegally funneling corporate contributions to individual candidates for the Texas Legislature as part of his drive to gain control of the State House. His goal was a legislature that would approve a redistricting map that would cement Republican control in Washington.