Gov. Mark White tonight called the Texas legislature into special session to deal with the state's budget deficit, which has reached $3 billion and is projected to soar even higher due to declining oil revenues and record-high, double-digit unemployment.

White, a Democrat, is seeking reelection this fall and is trailing his challenger, former Republican governor Bill Clements, in the polls. The special legislative session, to begin Aug. 6, is viewed by political analysts here as a risky but perhaps unavoidable step for the governor, whose popularity has been declining.

There is widespread disagreement among legislators about whether they should try to erase the deficit by raising taxes, severely cutting programs, doing both or doing neither. White has not come forward with a specific plan, but has said he will draft one before the legislature convenes.

In a four-minute televised address tonight, White said he would support budget cuts as long as they did not affect public school reforms. The only tax he mentioned was the income tax, which Texas does not have. It is almost a form of treason to speak kindly of an income tax in this state, and White made it clear he would not be charged with sedition.

The tax proposal most likely to move through the legislature, leaders in the House and the Senate say, is a one-cent rise in the state sales tax. There is also talk of putting a state lottery referendum on the November ballot. But a lottery and sales tax increase combined would do no more than halve the projected deficit.

Clements, who was governor from 1978 to 1982 before being defeated by White just as Texas was slipping into a recession, blasted his longtime antagonist for waiting so long to call the special session. "Back in January I urged Mark White to call the legislature back into session, and he tried to bury his head in the sand," Clements said. "A large part of the deficit now is due to his procrastination because this is a time-sensitive issue and the longer it goes forward, the bigger and worse the problem gets."

But Clements has had some difficulty trying to use the budget deficit to his political advantage. For several months, as he urged White to call the special session, Clements implied that he had a secret plan to resolve the deficit. When it became apparent that White was finally going to bring the legislators to Austin, and Clements was challenged to reveal his plan, he said that he never really had one, that it was a creation of the state press corps.

The Texas legislature, notorious for its colorful characters, if not statesmen, meets for six months every other year, which most state residents consider more than sufficient under normal circumstances.

The next regular session begins in January 1987, and White had hoped to avoid bringing the lawmakers back until then by eliciting 13 percent spending cutbacks from state agencies this year. But state comptroller Bob Bullock's deficit estimates grew increasingly bleak, and state treasurer Ann Richards expressed alarm that the state would be bouncing checks soon if action were delayed much longer.

"This is the toughest fight of our lives," White said tonight as he called the legislators back to Austin. "But Texans don't retreat from the battle. We join it. Tough times don't last, but tough people do. And Texans are tough people."