Since fund-raising times are tough in Texas, Rep. James M. Collins (R-Tex.) looked for only half a million dollars in Houston for his Senate campaign.

Not only is this the home of Collins' Democratic opponent, Sen. Lloyd Bentsen, but, as one Collins staffer noted: "Clements came in here with a vacuum cleaner and sucked every damn dime out of the town."

This reference was to Collins' cactus-tongued fellow Republican, Gov. Bill Clements, who, in his relentless fund raising at least, may be giving Bentsen and the Democrats more comfort than he is the GOP.

Untroubled by federal contribution limits in his statewide race, Clements is running for reelection with the kind of financial swagger that leaves other candidates in the state -- even multimillionaires like Collins -- looking like beggars with tin cups.

Last June Clements elevated the megabuck Texas fund-raiser to an art form by pulling $3.5 million out of a single meal here. He entertained about 3,300 supporters at dinner at $1,000 a plate and got checks in the mail from 200 more. President Reagan flew in to bless the transaction.

So Collins' own fund-raiser here a week ago had to be modest by comparison. It was just a little supper for some right-thinking folks: black tie, white chocolate mousse, tickets at $1,000, $500 and $250.

But Collins, a 62-year-old sagebrush conservative, hasn't survived eight terms in Congress by neglecting detail. Before it was over, it was a casebook example of how to put together such a dinner in Texas. The supporting cast included the vice president of the United States, a Texas millionaire oil wildcatter who operates in Indonesia and a Houston Toyota dealer who drives a Rolls Royce and looks like Johnny Cash.

As a Dallas congressman, Collins had no organization here in one of the world's major money markets and was not widely known. He needed not only money but also the sort of campaign commitments fund raising generates along with cash. John Decker, his finance director, also wanted an event early in the campaign "to produce a ripple effect that would bring us $500,000 out of Houston by election day."

Decker and others began thinking last March of a dinner in September or October for which the big draw would be Vice President Bush, a popular Houstonian and the last to give Bentsen a major challenge (in 1970). They learned that Bush would be in Houston Sept. 24 if Collins' campaign would pick up $8,000 of travel expenses.

They needed a coordinator. Collins' niece was active in the National Federation of Republican Women, whose Washington finance director, Lynda Stansbury, was getting restless. In June the Collins campaign hired her for four months to arrange one dinner that would shake the cash out of Houston.

Stansbury, 33, was a veteran of GOP campaigns in Virginia and Pennsylvania and had worked with the Republican National Committee's major donors program. In June she hit Houston cold. "We started with a list of about 500 previous donors from the 1970 Bush campaign," she said.

Decker added lists from legislative campaigns and from the Republican senatorial campaign committee. By Aug. 15 about 20 lists containing about 80,000 names had been merged by the campaign's computer into a core list of 10,000 prime donors in the Houston area.

Meanwhile, Collins persuaded an old friend from Southern Methodist University days, Roy M. Huffington, to serve as Houston finance chairman. Huffington, an amiable man of 64 worth about $100 million, is a former Exxon geologist with vast gas and oil holdings in Indonesia who spends nearly half his time in Asia.

With Huffington's help and name, Stansbury arranged four meet-the-candidate luncheons and one reception for Collins in Houston during July and August. Five hundred invitations went out to each event, followed by letters and phone calls.

About 50 people showed up for each, at which Collins spoke briefly, stressing his key campaign argument: Bentsen, rather than being a politically secure moderate, was actually a highly vulnerable liberal.

A controversial poll was circulated, showing Collins trailing Bentsen by 14 points statewide with 25 percent undecided, but leading Bentsen by 4 points among voters who knew them. The poll also showed Clements slipping in his reelection race, which did little to warm the strained relations between the two Republican camps.

The guests were asked to become dinner co-chairmen by buying or selling tickets for a table of eight. That would obligate each co-chairman to at least eight $250 tickets, equal to the $2,000 maximum donation allowable under federal law for one couple. Each co-chairman could either fill his table with $1,000 donors, or pay $2,000 for himself and his wife, invite six friends, and meet their commitment.

Clements had had it easier. With no limit on individual donations to candidates in state races, high rollers plunked down as much as $10,000 for a table and invited their friends. His $3.5 million dinner, according to a Clements campaign official, was the work of three people working fulltime for three months with Clements' political organization in five urban and 13 rural Texas regions. They recruited 255 dinner co-chairmen, each responsible for at least one $10,000 table.

The Collins campaign, with no such statewide structure, turned to direct mail. A 500-letter mailing Aug. 9 over Huffington's name went to potential co-chairmen, and another 200 letters Aug. 24 to business and political action committees in Houston. There was a 300-letter mailing over the name of Huffington's son Michael to business associates.

And there were three mass mailings of 10,000 letters each -- one Aug. 27 with invitations to what was now called "A Salute to George Bush"; a follow-up letter Sept. 23 ("George and Barbara Bush are coming home to Houston . . . . ") and one Sept. 13 over Collins' name updating dinner developments.

Some of the letters to potential co-chairmen went to Houston area "Eagles" -- heavyweight donors who annually give $10,000 or more to the Republican Party. One of the first to reply was Don McGill, 49, a Houston Toyota dealer with diamonds on his watchband.

McGill, who looks vaguely like Johnny Cash and drives a Rolls Royce once owned by Omar Shariff, not only bought a $1,000 ticket and buttonholed his friends, he put out an emotional, all points appeal on his agency's parts department teletype that links 124 Toyota dealers in five states. He sold 40 $1,000 tickets.

While 65 co-chairmen worked independently, six volunteers phoned eight hours a day for the final 10 days, reaching about 3,300 of the 10,000 on the potential donor list.

By Wednesday Stansbury had given the hotel a firm guarantee of 700 for the dinner, incuding a 7 percent underbuy for no-shows. Volunteer staff would fill any vacant seats and about 100 of the tickets would be given away, to the candidate's family, staff or local elected officials. One had been given to the hotel manager because, Stansbury reasoned, "If he's there the food and service will damn sure be right."

Against the gross from the dinner -- estimated now at $250,000 -- would be about $40,000 in dinner costs plus $16,000 in printing and postage.

The dinner was strip steak and snow peas, red wine and a giant glitter COLLINS against ceiling-high blue velvet. The band played Basie. Michael Huffington barely made it, having flown in from Indonesia in late afternoon.

The speeches began on time. Vice President Bush gave a strong endorsement of Collins, "my friend and a guy I respect," and wrapped things up promptly at 9 p.m. in time to make the TV news.

Outside the ballroom, the take was counted. A last-minute flurry of big contributions appeared likely to push the gross for the night over $300,000. As a result, Clements' $3.5 million yardstick was momentarily forgotten. CAPTION: Pictures 1 and 2, Rep. James M. Collins (R-Tex.), greets well-wishers at his fund-raising dinner. $1,000-a-ticket contributors line up to enter private reception for larger donors. Photos by Wendy Watriss for The Washington Post