THE MAN who is bailing us out of the worst financial failure in U.S. history, L. William Seidman, is the co-author (with Steven L. Skancke) of a new book extolling the American system. It's called "Productivity: The American Advantage." He sees no contradiction, although he appreciates the irony. The $500-billion debacle in the so-called thrift industry, was, he thinks, "an aberration."

He's going to write a book about it. He's made an outline. He writes a little on it every day. The heat is currently off the chairman of the Resolution Trust Corp. Since Aug. 2, when Saddam Hussein stormed into Kuwait, the Middle East has replaced the stinking S&L mess as the country's major preoccupation.

Americans are still trying to take in the full dimensions of the S&L scandal, the expense of the bailout -- and the perfidy of proprietors who dipped into the thrifts as if they were their personal honey pots. As L. J. Davis asks in a brilliant and witty history of the affair in the September Harper's, "Looted by its owner? Weren't most thrifts owned by you and me and the guy down the block, little guys like in 'It's a Wonderful Life'?"

"It's still a concern," says Seidman, over lunch in his splendid office with its wraparound view of capital monuments, "but it's not the main concern, the only concern, right now."

How long Seidman will remain in those quarters is a subject of much speculation in Washington. The White House, inexplicably, is trying to give him the bum's rush. Chief of Staff John Sununu is the leader of the "Seidman out now" forces, and Treasury Secretary Nicholas Brady is also in the front ranks.

Seidman is a man singularly without rancor. He keeps on the wall a picture of the horse that recently threw him -- and broke his pelvis -- during a ride at his New Mexico ranch. So he is philosophical about the eviction talk.

"I was a Reagan appointee -- they probably want their own person here," he says tolerantly. "And then they wanted to have the chairman of the RTC subject to removal by the White House, and I opposed it. I think the chairman should be independent. One reason the Federal Deposit Insurance Corp. {the FDIC, which Seidman once headed} worked is because it was independent." Seidman is a weatherbeaten 69 and hardy. He bicycles almost three miles between his Georgetown house and his office morning and night. He knows that the candor that endears him to Congress and the press enrages the White House. But his reputation is golden -- back to his days in the Ford White House -- and he is expected to take his own time about leaving.

Discovering the extent of the mess has not diminished his faith in the system, which he thinks will show the Japanese in the '90s how much better a classless, multi-racial society works because it is more responsive to the social and business needs of its citizens. And although the S&L crisis would argue otherwise, the American system has a self-correcting mechanism.

The reason the mechanism didn't work in the S&L business is because there was no political opposition to thrift deregulation.

"The Democrats and Republicans agreed on what was to be done, for entirely different reasons. The Republicans were in favor of deregulation, even in institutions with federally guaranteed deposits. The Democrats wanted to do anything they could for their friends in housing and the thrift industry. Republicans like banks; Democrats like S&Ls, the little man's bank where he gets money for his house."

So the crisis never got into politics, which is where all crises belong.

Neither side saw an advantage in bringing up the problem in the 1988 election -- the Republicans because it happened on their watch, the Democrats because too many of their own, beginning with Speaker Jim Wright, were involved. Four of the "Keating Five" are Democrats; their interventions on behalf of Charles Keating, the S&L king who was so generous with campaign contributions, are an embarrassment to the party.

When Ed Gray, the head of the Federal Home Loan Bank Board -- and a hard-core Reaganite who genuinely wanted to see no evil -- felt he had to warn the Reagan White House that the unregulated high flyers were in the process of bankrupting the country, he was snubbed by former OMB director David Stockman and reproached by his deputy, Constance Horner. "She gave him the ultimate insult -- she called him a re-regulator."

Congress wouldn't listen, either. A smear campaign about Gray's expense accounts was mounted -- "to keep people from listening to what he was saying," says Seidman. Deprived of the manpower to examine the horrendous records of the lying, cheating, stealing industry, Gray was forced out of office.

The thrift industry hurtled merrily towards ruin.

"It was like building a nuclear plant without safety devices," says Seidman. "If you don't have them, it is going to melt down and take you with it."

Mary McGrory is a Washington Post columnist.