Lawyers defending the Israeli prime minister against a web of corruption allegations launched their cross examination of a key witness Thursday by painting him as a lying, litigious businessman with an unsavory reputation and a faulty memory.

American Jewish businessman Morris Talansky did major political, if not legal, damage to Ehud Olmert last month by alleging that the Israeli leader accepted hundreds of thousands of dollars in cash. According to the original accusations, Olmert received the cash as bribes or illegal campaign financing, and used it in part to fund his high living.

Olmert’s lawyers also tried to erode the credibility of law enforcement authorities by suggesting that, in their zeal to nail the prime minister, they alternately intimidated Talansky and offered him special treatment.

The outrage provoked by Talansky’s testimony in May seriously damaged Olmert’s credibility and prompted his Kadima Party to set new leadership elections, to be held by Sept. 25.

Olmert has denied wrongdoing but promised to resign if indicted. If he has any chance of surviving politically, the effort to discredit Talansky might be his only lifeline.

Olmert’s allies note that he’s been written off before but has managed to emerge intact. He has survived four other corruption probes since he became prime minister in 2006. And he held onto his job even though he was widely perceived as bungling a monthlong war against Lebanon’s Hezbollah guerrillas in 2006.

If Olmert were to leave office prematurely, it could hamper Israel’s efforts to make peace with the Palestinians and Syria.

The 75-year-old Talansky appeared nervous throughout much of the cross-examination Thursday, drumming his fingers on the table, fidgeting with a plastic cup and at one point asking for a break. He offered contradictory statements and at times was unable to remember dates, sums and the details of litigation he had been involved in.

Lawyers spent more than six hours grilling him about previous testimony and attempted to undermine his credibility by pointing out contradictions in his statements.

During his testimony, Talansky acknowledged that his memory might not always have served him well on details of dates and sums. But he insisted that “I don’t believe I invented stories” and that “the totality” of his accounts was accurate.

Olmert lawyer Eli Zohar questioned Talansky at length about multiple lawsuits he has filed in the U.S. Zohar cited witnesses who accused Talansky of hitting an elderly dentist and hiring thugs to go after a person who owed him money. Talansky denied both allegations.

Zohar also brought up Talansky’s efforts to win a $3 million severance package from a Jerusalem hospital where he was employed as a fundraiser for more than 20 years. Talansky denied the hospital board’s allegations that he forged a document promising him such a fat package.

The cross-examination is expected to take five days.

Talansky’s lawyer, Jacques Chen, said the defense didn’t even come close to eroding his client’s credibility.

“We sat there for a whole day from 9 until 4 and we heard stories from across the ocean,” Chen said. “I have to say that it was quite boring.”

Olmert’s lawyers also assailed the credibility of police and prosecutors investigating the prime minister. Recounting Talansky’s tirade in May against what he characterized as police hectoring, they asked him if he might have just thrown out answers to get the interrogators off his back. Talansky said at times he felt police were trying to get him to say certain unspecified things but he “didn’t follow them.”

Earlier, however, he testified that “sometimes you say things just to get rid of it.”

In a separate corruption case against Olmert, police last week accused him of pocketing thousands of dollars by deceiving multiple sources _ including organizations for Holocaust survivors _ into paying for the same trips abroad.

Olmert has called the accusations “distorted,” charging the police and state prosecutors with trying to bring him down.