With Democrat Ann Richards apparently closing the gap on Republican Clayton Williams in the Texas governor's race, political analysts are now looking to the state's Mexican-American vote as a key to the election.

That is not necessarily good news for Richards. Many South Texas activists say she has failed to galvanize the largely Hispanic electorate from San Antonio south to the Rio Grande Valley, leaving a vacuum that Williams filled over the past six months. If he gets 30 to 40 percent of the South Texas vote, where Democrats traditionally win by big margins, it might negate Richards's recent gains among upscale GOP voters in Dallas and Houston.

To counteract Spanish-language ads that Williams has run in South Texas, the Texas Democratic Party this week began airing radio commercials in Spanish that ridicule Williams and the Republican Party's new-found interest in Hispanic voters. One exchange in the spot goes like this:

Voice One: "Oh, yes. Always have lots of respect for the Mexican women . . . . "

Voice Two: "Liar! The Republican candidate for governor has told us he traveled to Mexico to be 'serviced' by women. How is this for respect?"

Voice One: "Oh, yeah. Me, your Republican candidate, can sing with mariachis and speak Spanish more better."

Gordon Hensley, Williams's spokesman, called the ad "slanderous and insulting" -- a relatively mild rejoinder in Texas this year.

The Williams camp is especially upset that the commercial implies he supports the English Only movement in Texas, which, although once endorsed at a state GOP convention, has been disavowed by Williams and was taken out of the platform this year.