AUSTIN, TEXAS -- Dallas financier and heavyweight political fund-raiser Jess Hay next week will join other substantial citizens in endorsing Sen. Albert Gore Jr. in perhaps the last gasp of the Tory establishment that once controlled Texas Democratic politics.

While Gore admittedly is not their first choice for president, he is the closest Democrat to their model of a centrist able to carry Texas and the South. But in his new role, he confronts liberal party activists who have dominated recent state Democratic primaries for every office except governor.

Whatever happens to Gore's long-shot presidential bid, his campaign here in the March 8 Super Tuesday primary is central to this politically critical state's future. He looks like the last windbreak against cyclonic party realignment, joining Texas to polarized national parities -- liberal Democratic and conservative Republican.

That is a peculiar mission for 39-year-old Al Gore, who only last summer seemed an archetypal southern liberal. His sole significant Texas booster was ex-railroad commissioner Buddy Temple, a key 1984 backer of Walter F. Mondale and member of Impact '88 (Democratic money men who wanted Mario Cuomo and settled for Gore).

Two developments broadened Gore's base. First was the fall of Gary Hart, supported in Texas by a potent liberal-Tory coalition. Second was Gore's emergence as the Voice of the South once Sam Nunn and Chuck Robb declined, changing his emphasis from environmental protector to defense hawk. Finally, when Rep. Richard Gephardt virtually abandoned Texas to concentrate on the Iowa caucuses, his prospects here vanished.

The upshot was Gore's endorsement by party stalwarts such as Democratic State Chairman Robert Slagle and ex-state chairman Calvin Guest. That did not impress State Attorney General Jim Mattox, far ahead in the early going for the 1990 nomination for governor.

Combative and populist, Mattox represents the new left-leaning face of Texas Democrats, and contends Gore's backers can't nominate anybody here. ''They march to a different drummer than mainstream Democrats here, and nobody's following them,'' he told us. Liberal activists, who dominate the Texas primary, have no interest in Gore.

One Gore backer who does generate Mattox's respect is Jess Hay, and that's because of the color green. Hay guarantees an impressive war chest. His first choice was Nunn, his second was Sen. Bill Bradley and he is really not sure whether Gore can be nominated. But Hay considers him the only willing candidate who can be elected.

He is not alone. Former Democratic national chairman Robert Strauss, while unlikely to endorse any time soon, has been talking up Gore around the nation and with fellow Texans such as Hay. Powerful State House Speaker Gib Lewis joins Gore this week.

All this confronts the labor/minority group/trial lawyers/teachers coalition that has revolutionized Democratic politics throughout the South. With no slight interest shown in Hart's rebirth, the coalition is choosing between Sen. Paul Simon and Gov. Michael Dukakis.

Mattox is particularly attracted to Simon, once his seatmate on the House Budget Committee in Washington. He hints that he and his fellow populist, State Agriculture Commissioner Jim Hightower, might endorse together -- maybe for Simon. Influential state senator Ray Farabee, once Hart's main Texan, now backs Simon. Lt. Gov. Bill Hobby is staying neutral after the embarrassment of supporting Hart, but friends say he likes Simon.

Yet Simon may already have started downhill. State Treasurer Ann Richards, heroine of the liberals, wonders about Simon. After hearing him describe Harry Truman as his political role model, she was stunned to hear that Simon as a young weekly newspaper editor in Illinois endorsed Thomas E. Dewey for president in 1948. She speculates how he can square crusading for federal spending programs with backing Gramm-Rudman deficit reduction. He blundered a week ago by turning nuclear hawkish in an Austin speech.

That leaves Dukakis, who as an ethnic liberal from the Northeast would seem poorly suited to Texas. In fact, the primary here is both liberal and ethnic. He is favored by the Jewish community and is way ahead for the big Hispanic vote. Dukakis vs. Gore could be the shootout to determine what this state's Democratic Party will look like.

Hay believes Sen. John Glenn would have defeated Mondale in Texas four years ago if he had survived long enough to get here, and therefore is thankful Gore has finessed Iowa and New Hampshire to be ready for Super Tuesday. With the black vote wrapped up by Jesse Jackson, Tory Democrats have a last chance to win most white voters and, therefore, the primary. If they can't, their long battle against a two-party realignment here may be over.