The prosecution struggled to salvage the credibility of its star witness against former D.C. Superior Court Judge Robert H. Campbell yesterday after his testimony was badly battered by defense lawyers during two days of cross-examination.

The government's bribery charge against Campbell rests heavily on that witness, Robert Payne Jenkins, once a top executive of a local construction firm, who has testified that he made 10 to 15 cash payoffs to the former judge to gain lenient disposition of tickets issued for alleged overloading of trucks by the firm.

From the outset of the trial in U.S. District Court, the government told the jury that Jenkins would be a "hostile" witness for the government, that he remained a "company man" despite the fact that he was fired last fall by his company, Excavation Construction Inc. of Bladensburg.

Yesterday afternoon, assistant U.S. Attorney John P. Hume began shouting questions at Jenkins when it was finally time for the government to reexamine its own witness. His intention, it appeared to courtroom observers, was to rehabilitate Jenkins' testimony.

Defense lawyers all emphasized their theory that the government had charted an alleged bribery scheme for Jenkins' benefit, and then persuaded him that its version was factual. Jenkins, the defense argues, was a willing witness, fearful that he might otherwise go to jail on an earlier perjury conviction in connection with the Campbell investigation.

Jenkins, a tall, expressionless man who testified in a dull, flat voice, acknowledged to defense lawyer R. Kenneth Mundy yesterday that at one point he told investigators to write down what they wanted him to say and he would see if he could say it. The government refused, Jenkins testified. Mundy finished off his questions to Jenkins, who is unemployed, by drawing his concession that the government had "offered to be helpful" as a reference in his hunt for a job.

Questioned later by Hume, Jenkins, who was granted immunity from prosecution on any charge except perjury, testified that no one had suggested to him that he tell the jury anything but the truth about the Campbell case.

Former Judge Campbell, Larry A. Campbell (no relation to the judge), the general manager of Excavation Construction, and the firm itself are all charged with conspiracy, bribery and racketeering.

The defense, using a large posterboard chart, emphasized that Jenkins had met 13 times with federal investigators for nearly 40 hours of discussion after he agreed to cooperate with them. Before the proceedings were adjourned yesterday, Hume began a series of questions of Jenkins that seemed designed to show that the fundamental allegations in the case -- that bribe payments and favors were done for the judge -- were disclosed by Jenkins to investigators early on in that series of meetings.

Jenkins had also testified during defense questioning that the company money he had identified as possible bribe payments to Campbell could have been cash that he withdrew from business accounts to pay for his own expenses, particularly for travel.

In an attempt to counter that argument, Hume showed Jenkins one of his withdrawal vouchers that had credit card receipts attached to it that specifically related to travel expenses. Hume showed several other vouchers to Jenkins -- for monies drawn during the time bribes allegedly were paid -- that had no such receipts attached.

The trial, before Judge Thomas A. Flannery, is scheduled to resume Monday and is expected to last at least two more weeks.