Texas Gov. Bill Clements has made a career out of confounding political opponents, and when more than 3,000 supporters gather in Houston tonight for a $1,000-a-plate fund-raiser, the public will be treated to another example.

The main attraction at the $3 million dinner, principal fund-raising event of the campaign for Clements, is President Reagan. Former president Ford also may attend.

But the real spectacle may be an assortment of former Democratic officeholders in Texas who have signed up with Clements in his bid for reelection as the first Republican governor of Texas in a century.

Among them are former governors Preston Smith and Allan Shivers, plus John Connally, who was a Democrat before switching to the GOP. In addition, the campaign is expected to announce the endorsement by former governor Price Daniel at tonight's dinner.

Clements also expects to receive support of several former Democratic attorneys general in his race against Mark White, the incumbent attorney general.

Through this strategy, Clements is attempting to redefine the November election away from his party label, which has been historically alien to most Texans, and focusing on the conservative-liberal definitions that many are still more comfortable with.

And while Clements remains identified in the public mind with the policies and personality of Ronald Reagan, he has staked out a position of independence from the president that could prove useful if conditions in Texas worsen between now and November.

Unemployment in Texas is 6.4 percent, up more than a point in the last year. More importantly, there is a growing perception among Texans that the national recession has suddenly descended on them and they are sending signals to the rest of the country that they are not prepared to provide jobs to unemployed workers from other states.

All this complicates Clements' reelection chances, especially in a state that remains overwhelmingly Democratic in registration if not philosophy and voting habit. Clements is hoping to capitalize on Reagan's popularity without having to suffer the consequences if the president's popularity continues to decline in the state.

By nature, Clements is an independent politician, brusque and blunt, who is no less afraid to attack the president than his Democratic opponents. Over the past 18 months, he has publicly differed with Reagan on a variety of policy matters, from implementation of Reagan's New Federalism to tuition tax credits to the administration's immigration policy.

Clements has done this while enjoying extraordinary access to Reagan and his Cabinet. He has used his political entree to lobby the administration on the massive prison reform lawsuit that has been brought against the state, and the Justice Department's position on the right of the children of undocumented workers to public education.

Four years ago, Clements campaigned for governor promising to help defeat President Carter, and he stumped the state in 1980 in Reagan's behalf.

Now Democrats hope to turn that association back on Clements by linking him to the economic woes afflicting the state.

Recent polls in Texas show that Reagan's popularity, while still quite high, has declined, and even Clements has acknowledged it.

Clements' advisers believe that at this point Reagan is not necessarily an asset to the governor in the fall campaign, but hardly a liability either.

But the Democrats believe Clements is deliberately attempting to put more distance between himself and the president in order to build a record of independence for November.

In response, Clements' campaign staff chalks this up to smart politics.

"Gov. Clements supports the president," said George Bayoud, Clements' finance director, "but when he disagrees with him, he'll say it. Texans want him to be that way and that's the way Bill Clements is."

Tonight's fund-raiser has long been planned not only as an event that will raise at least $3 million for Clements' campaign chest, but also as a psychological attack on the Democrats who are strapped for funds.

Four years ago, Clements spent about $7 million to win election and is prepared to spend at least that much this year, if necessary.

But the added surprise of the Democratic endorsements has added an unexpected twist to tonight's event.

"We want everybody's support," Bayoud said. "In Texas, you have to have that attitude."