As Lloyd Blankfein prepares to testify today that Goldman Sachs is innocent of allegations that the company knowingly sold bad products to clients, Senate investigators are saying that Abacus was just the tip of the iceberg. Stay tuned for fireworks:

In a statement prepared for the hearing and released on Monday, Mr. Blankfein said the news 10 days ago that the S.E.C. had filed a civil fraud suit against Goldman had shaken the bank’s employees.

“It was one of the worst days of my professional life, as I know it was for every person at our firm,” Mr. Blankfein said. “We have been a client-centered firm for 140 years, and if our clients believe that we don’t deserve their trust we cannot survive.”

Mr. Blankfein will also testify that Goldman did not have a substantial, consistent short position in the mortgage market.

But at the press briefing in Washington, Carl Levin, the Democrat of Michigan who heads the Senate committee, insisted that Goldman had bet against its clients repeatedly. He held up a binder the size of two breadboxes that he said contained copies of e-mail messages and other documents that showed Goldman had put its own interests first.

“The evidence shows that Goldman repeatedly put its own interests and profits ahead of the interests of its clients,” Mr. Levin said.

Mr. Levin’s investigative staff released a summary of those documents, which are to be released in full on Tuesday. The summary included information on Abacus as well as new details about other complex mortgage deals.

On a page titled “The Goldman Sachs Conveyor Belt,” the subcommittee described five other transactions beyond the Abacus investment.

One, called Hudson Mezzanine, was put together in the fall of 2006 expressly as a way to create more short positions for Goldman, the subcommittee claims. The $2 billion deal was one of the first for which Goldman sales staff began to face dubious clients, according to former Goldman employees.

“Here we are selling this, but we think the market is going the other way,” a former Goldman salesman told The New York Times in December.