Donald Trump’s defense team attacked the credibility of prosecutors’ first witness in his hush money case on Friday, seeking to discredit testimony detailing a scheme to bury negative stories to protect the Republican’s 2016 presidential campaign.

On the witness stand for a fourth day, former National Enquirer publisher David Pecker was grilled about his memory and past statements as the defense tried to poke holes in potentially crucial testimony in the first criminal trial of a former American president.

Two other witnesses followed Pecker as prosecutors built the foundation of their case involving a hush money payment to porn actor Stormy Daniels, who claimed she had a sexual encounter with Trump. Trump’s longtime executive assistant told jurors she recalled seeing Daniels in a reception area of Trump Tower, though the date of the visit wasn’t clear.

Pecker’s testimony provided jurors with a stunning inside look at the supermarket tabloid’s “catch-and-kill” practice of purchasing the rights to stories so they never see the light of day. He’s believed to be a key witness to bolster prosecutors’ theory that Trump sought to illegally influence the 2016 race by suppressing negative stories about his personal life.

Trump, who denies any wrongdoing, slammed the prosecution as he left the courthouse Friday after spending most of the week in his role as criminal defendant instead of political candidate. Trump seized on President Joe Biden’s remarks Friday that he’s willing to debate Trump. Trump told reporters he’s up for it anytime, anywhere.

Under cross-examination, Trump’s lawyers appeared to be laying the groundwork to make the argument that any dealings Trump had with Pecker were intended to protect Trump, his reputation and his family — not his campaign. The defense also sought to show that the National Enquirer was publishing negative stories about Trump’s 2016 rival, Hillary Clinton, long before an August 2015 meeting that is central to the case.

During that meeting, Pecker said he told Trump and then-Trump attorney Michael Cohen he would be the “eyes and ears” of the campaign, and would notify Cohen if he heard negative stories about Trump so they could be killed.

Under questioning by Trump lawyer Emil Bove, Pecker acknowledged there was no mention at that meeting of the term “catch-and-kill.” Nor was there discussion at the meeting of any “financial dimension,” such as the National Enquirer paying people on Trump’s behalf for the rights to their stories, Pecker said.