– Benjamin Netanyahu has survived many challenges on his way to becoming the second-longest-serving prime minister in Israeli history. A deepening criminal investigation now presents a threat to his grip on power.

Police questioned Netanyahu twice in recent weeks over his receipt of gifts from businessmen and for reportedly plotting to help a newspaper owner in return for favorable coverage. He denies any wrongdoing. But with a steady drip of leaks from the probes dominating daily headlines, opposition parties are calling for him to go and the allegations are beginning to weaken him, even within his own ranks, said Eytan Gilboa, director of Bar-Ilan University's center for international communications.

"It's clear that some members of his party are seeing this and beginning their preparations to try to become the next leader," Gilboa said. "The opposition obviously is trying to capitalize on this moment."

The probes raise the pressure on Netanyahu after last month's diplomatic debacle at the United Nations, where the Security Council declared Israeli settlements illegal and described land won in the 1967 Middle East war as occupied Palestinian territory. Then came a blistering critique from Secretary of State John Kerry, who called Netanyahu's government the most right-wing in Israeli history and said settlers were dictating its agenda.

But what has really electrified Netanyahu's opponents is the inquiry, which is exposing how the premier received valuable gifts from Israeli and foreign businessmen he says are simply generous friends.

Calls for Netanyahu's resignation grew as Israel's Channel 2 television reported that police have a tape of Netanyahu trying to end a feud with Yedioth Ahronoth newspaper owner Arnon Mozes by discussing how to undermine Israel Hayom, a free publication backed by U.S. casino mogul Sheldon Adelson, a Netanyahu patron.

Channel 2 reported Tuesday night that in exchange for passing a law forcing Israel Hayom to charge customers money — a step likely to limit its readership — Mozes promised to do all he could through Yedioth to keep Netanyahu in power. In the end, the press law was never passed.

Police are planning a third round of questioning soon, Israeli media reported.

"The prime minister cannot stay in office even one more moment," said Zehava Galon, chairwoman of the opposition Meretz party. "Coordinating benefits with a media outlet for positive coverage is governmental blackmailing. Netanyahu acts like a wheeler-dealer and it proves that he has been prime minister for too long. He should resign."

Netanyahu's attorney, Jacob Weinroth, did not dispute the reported gifts but said there's nothing illegal in accepting presents from friends.

Netanyahu told ministers from his Likud Party on Sunday that he is innocent of any wrongdoing, and portrayed the probes as a witch hunt.