The election is three years away, but the two leading contenders in the 1990 Texas gubernatorial contest already have taken themselves out of the race. San Antonio Mayor Henry Cisneros -- considered the Democratic front-runner after Lt. Gov. Bill Hobby decided several weeks ago against running -- said this week he will not seek the governorship or any statewide office in 1990. He cited the health of his infant son, born two months ago with severe birth defects.

"The family stresses associated with John Paul's care require attention that is not compatible with gearing up for a major statewide effort," Cisneros said.

Cisneros said he made his decision now so supporters could commit to other candidates. With Cisneros out, state Treasurer Ann Richards is under increased pressure to join the race. All-but-announced candidate Attorney General Jim Mattox called Cisneros' decision "a tremendous boost for me."

Cisneros said his decision "will allow me to tackle some very challenging issues in San Antonio . . . without opponents damaging those efforts for reasons of wanting to cripple a campaign for higher office." Cisneros, whose fourth term ends in April 1989, did not say if he will run for another term as mayor.

Ruben Bonilla, a Democratic Hispanic leader, said Cisneros' decision is disappointing to Hispanics, but added, "By no means is Henry Cisneros' obituary being written today."