Governor-elect William P. Clements, a wealthy but once obscure oil drilling contractor, committed more than $4.5 million of his own fortune to finance a $7 million election campaign-perhaps the biggest election money pot nationwide in the 1978 campaigns.

The spending by Clements, the state's first Republican governor in 104 years, set the pace for a towering $20 million in Texas's statwide election spending this year-almost $9 for every vote cast in the Nov. 7 election, according to freshly filed campaign finance reports.

"Texas never does anything small," said Fred Wertheimer of Common Cause, the Washington-based political monitoring group. "They obviously saw that in 1978 they would have to set their standards exorbitantly high, and they more than exceeded themselves."

Wertheimer said that Clements' $4.5 million-plus in personally guaranteed loans from several Dallas banks "breaks the bank at Monte Carlo as far as public records are kept."

Clements places his net worth at $29.4 million, and Wertheimer said the guaranteed loans "really demonstrate the incredible advantage a wealthy person has under a private [campaign] financing system-an enormous, unfair advantage."

But a spokesman for Clements says that such an amount was needed for an obscure, politically unknown candidate to overcome the advantages of his opponent, Democratic Attorney General John Hill.

Too, the vastness of the state-EI Paso is closer to Los Angeles than it is to Dallas-makes for heavy traveling costs, and a century of one-party control here has traditionally given Democratic candidates a sizable advantage.

Hill, according to campaign reports received by the secretary of state, spent $2,825,115 on his losing campaign, compared with Clements' $7,189,772. Clements won by less than 1 percent out of $2.3 million votes cast.

In other races, Sen. John G. Tower (R-Tex), until Clements' election Texas' only statewide Republican officeholder, spent $4.3 million in his narrow election to a third term. His Democratic opponent, Rep. Robert C. Krueger, spent $2.4 million in his campaign, the closest reelection contest Tower has faced.

Nearly $20 million was spent by general election candidates in just the top three races-for senator, governor and attorney general. In addition vast sums were spent in last spring's primary by those who never made it to the general election-including Gov. Dolph Briscoe's $3 million primary loss to Hill.

Much of Clements' money went to such traditional campaign efforts as telephone banks (33 made 875,192 calls) and in organizing campaign committees in every country of the state, some of which hadn't seen Republicans since Reconstruction.

The telephone banks were a key part of the Clements' campaign efforts to get out the vote, and apparently helped, since Hill was hurt by low Democratic voter turnout, among other things.

Clements' $7 million campaign was more than Sen. Henry M. Jackson (D-Wash) spent in his 197l presidential nomination effort. It was also expected to be a bit less than Sen. Jesse A. Helms (R-N.C.) spent in his reelection campaign this year, but Wertheimer said Helms spent "huge amounts for fund-raising."

Wertheimer wryly added: "Clements' campaign costs were limited to tapping himself on the shoulder and writing himself a check," said therefore he had more total funds left over to campaign on.

Most of Clements' loans, according to finance reports, came from the Republic National Bank and the First National Bank of Dallas. They were personally guaranteed by Clements, but there were costs to this "fund-raising."

For example, Clements' final election report, covering the Oct. 29 to Dec. 2 period, shows a $41,990.41 interest payment to Republic and $54,438.35 to First National.

The Clements campaign has said it expects to try to raise funds to pay off the loans, so it is not known how much of the $4.5 million-plus will eventually come out of Clements' pocket. But if he raises as much after the election as he did before-about $2.7 million-it still won't be enough.

And Clements will have to tap himself on the shoulder again, this time for keeps.