NEW YORK — A veteran tabloid publisher testified Tuesday that he pledged to be Donald Trump ‘s “eyes and ears” during his 2016 presidential campaign, recounting how he promised the then-candidate that he would help suppress harmful stories and even arranged to purchase the silence of a doorman.

The testimony from David Pecker was designed to bolster the prosecution’s premise of a decades-long friendship between Trump and the former publisher of the National Enquirer that culminated in an agreement to give the candidate’s lawyer a heads-up on negative tips and stories so they could be quashed.

The effort to suppress unflattering information was designed to illegally influence the election, prosecutors have alleged in striving to elevate the gravity of the first trial of a former American president and the first of four criminal cases against Trump to reach a jury.

Pecker is the first witness against Trump, who faces 34 felony counts of falsifying business records in connection with hush money payments meant to prevent harmful stories from surfacing in the final days of the 2016 campaign.

With Trump sitting just feet away in the courtroom, Pecker detailed his intimate, behind-the-scenes involvement in Trump’s rise from political novice to the Republican nomination and the White House.

Pecker traced the origins of their relationship to a 1980s meeting at Trump’s Mar-a-Lago estate in Palm Beach, Florida, and said the friendship bloomed alongside the success of the real estate developer’s TV show “The Apprentice.”

Their ties were solidified during a pivotal August 2015 meeting at Trump Tower involving Trump, his lawyer and personal fixer Michael Cohen, and another aide, Hope Hicks, in which Pecker was asked what he and the publications he led could do for the campaign.

Pecker said he volunteered to publish positive stories about Trump and negative stories about his opponents. But that wasn’t all, he said, telling jurors how he told Trump: “I will be your eyes and ears.”

“I said that anything I hear in the marketplace, if I hear anything negative about yourself, or if I hear about women selling stories, I would notify Michael Cohen,” so that the rights could be purchased and the stories could be killed.

“So they would not get published?” asked prosecutor Joshua Steinglass.

“So they would not get published,” Pecker replied.

Pecker’s testimony Tuesday followed a hearing earlier in the day in which prosecutors urged Judge Juan M. Merchan to hold Trump in contempt and fine him $1,000 for each of 10 social media posts that they say violated an earlier gag order barring attacks on witnesses, jurors and others involved in the case.

Merchan did not immediately rule, but he seemed skeptical of defense arguments that Trump was merely responding in his posts to others’ attacks and had been trying to comply with the order.