WASHINGTON – Barack Obama caught up to his rival Friday in the scramble for superdelegates, a major symbolic blow to Hillary Rodham Clinton's claim that she can still win the Democratic presidential nomination.

But the 13 Texans already in her camp held firm, and she countered late in the day by adding a San Antonio congressman, Ciro Rodriguez, to her endorsement list.

And three other Texas congressmen wrote party leaders to urge patience.

"We're still going forward. ... There's still six more states to be decided," said Rep. Henry Cuellar, D-Laredo.

Mrs. Clinton's top strategist insisted Friday that she'll stick it out through the last primary June 3 and is even willing to continue campaigning through the summer if neither candidate has collected a majority of delegates. But losing the superdelegate lead, Mrs. Clinton's team struggled to shake off a sense of inevitable defeat.

"It's on life support," said Sue Lovell of Houston, a Democratic National Committee member who supports Mrs. Clinton and doesn't think she should quit. She said she'll stick with Mrs. Clinton until she wins or releases her delegates from their pledges of support.

But Ms. Lovell worries that Obama backers in Texas and elsewhere will try to purge the party leadership of anyone who stayed neutral or backed his rival. "Then it becomes personal. It would make it hard to be unified," she said.

The tussle for superdelegates – the party leaders, governors and lawmakers who get automatic convention votes – has turned into nothing less than psychological warfare.

Thanks to Mr. Rodriguez, Mrs. Clinton now has a 14-12 edge among the Texans, with six more staying neutral. She won the state's March 4 primary, though Mr. Obama is poised to win the caucus process that will allocate part of Texas' delegates, so he could win more delegates overall from the state.

With Mrs. Clinton refusing to surrender before the last primaries, Mr. Obama can force her from the race only by locking up the nomination. On Friday, he added nine superdelegates to his tally, including one Clinton defector.

Clinton aides argued that in swing states with lots of blue-collar whites, such as Pennsylvania, Ohio and Michigan, and in swing districts, Mrs. Clinton would be far stronger against GOP Sen. John McCain.

"We're not oblivious to the environment in which we're operating," said her top strategist, Geoff Garin, but "Sen. Clinton is in a better position to win the general election."

Mr. Cuellar was one of 16 House members who signed a letter to other party leaders, urging them to keep in mind the superior drawing power Mrs. Clinton has shown in bellwether states and among swing voters.

Her April 22 victory in Pennsylvania "was not just a victory for Hillary Clinton. It was also a wake-up call for superdelegates," said the letter, also signed by Rep. Gene Green of Houston and House Intelligence Committee Chairman Silvestre Reyes of El Paso.

Mr. Obama's surge in superdelegates was no accident. David Hardt of Dallas, president of the Young Democrats of America, described a "hard pitch" via phone calls and e-mails.

The head of Mr. Obama's college and youth outreach effort called on leaders of the Young Democrats and College Democrats of America "to certify the will of young voters across the country by uniting behind Barack Obama."

"Both campaigns have been actively courting my organization," Mr. Hardt said Friday, but he is staying neutral.

Mr. Green, the Clinton-backing Houston congressman whose district is two-thirds Hispanic, said Mr. Obama has more work ahead of him than merely finding ways to match the Clinton appeal among working-class whites in the Rust Belt.

"In the Hispanic community, he has problems," he said. "He has to reach out to everyone."

Mr. Cuellar agreed with Mr. Green that he would support Mr. Obama if he becomes the nominee, "but it's not that automatic." He cited a lack of outreach to Hispanics, the lack of familiarity with border issues Mr. Obama showed during the Texas primary, and his views on trade.