SAN ANTONIO -- Bill Clements, the first Republican governor of Texas since Reconstruction, is the campaign's central and probably only issue. It is not so much the incumbent's party as it is his personality, which can most charitably be called "contentious." Bill Clements and humility are total strangers.

On Nov. 2, the election will probably be decided by whether more Texas voters see the governor as tough rather than mean, or arrogant rather than self-confident. The Clements campaign is spending money at will; about $3 million will buy TV and radio spots.

Mark White, in his own $1.9 million media buy, promises to "listen," which he accuses Clements of failing to do. White, a conservative who appears uncomfortable in his mildly populist campaign, also accuses the governor of giving aid and comfort to utility companies and usurers. Hasizeis objective is similar to Shamie's in Massachusetts, though his chances are much better. (White defeated present White House Chief of Staff Jim Baker to become the state's attorney general in 1978.)

In spite of the bundle being dropped in paid media, the free media are crucial in Texas. Both candidates agreed to participate in TV debates, which have become the wild card in television-age politics. Politicians believe the prospect of televised debates suspends voters' decision- making processes. While waiting to see the competitors face off in their living rooms, voters tend to discount whatever paid media crosses their line of vision.

In the first televised debate between these Texas contestants, White accused Clements of unfair campaign practices and general meanness. (In his own campaign newspaper, Clements had made an issue of the fact that 19 years ago, when a law student, White had once been arrested for drunk driving.) White succeeded in provoking flashes of temper from Clements, in contrast to the governor's TV spots, which have sought to humanize the Republican executive. In their second debate Clements did not lose his cool.

Texas is still a Democratic state so the Clements commercials stress the governor's endorsement by three former Democractic governors who, upon closer examination, turn out to be more former than Democratic: Former governor Alan Shivers endorsed Ike over Adlai Stevenson in 1952 and never returned to the party; former governor Preston Smith sought renomination in 1972 and won only 8 percent of the Democratic primary vote, and former governor John Connally, field marshal (ret.) of Democrats for Nixon.

Clements has avoided one common pitfall by unifying his paid commercials with his free media coverage. Frequently the eloquent candidate in the well-produced commercial at 10:30 p.m. can sound, in an unrehearsed appearance on the 11 o'clock news, like Rodney Dangerfield.

If not eloquent, at least Clements is consistent. He insists in debates, speeches and commercials alike that he is "not a politician but a businessman." Texas businessmen, he says in his speeches and commericals, have created four out of every 10 new jobs created in all of the United States since he became governor in 1979. In one of his commercials, Clements says: "Texas is strong, becoming stronger . . . full of hope, hard work and opportunity. That's what I was raised on and that's what I believe in." In the closing statement of his debate, Clements said: "Texas is strong, becoming stronger, "etc.

In the closing days of the campaign, White has turned to old-fashioned class warfare with a commercial that begins with a lavish formal dinner party heavy on the candelabra and caviar. No faces are visible, just opulent clothes and grub -- and no good ole boys. That scene gives way to a picture of White standing on the street of a Texas town. He reminds viewers that Clements has called Texas unemployment "insignificant," and says Texans don't need a governor who listens to the big shots on Wall Street -- they need a governor who cares about the people on Main Street.

As somebody -- I think it was either Burgess or Don Meredith -- once said: You can tell an awful lot about any candidate by his TV commercials.