Israeli Prime Minister Benjamin Netanyahu is at the top of his political game.

He is revelling in the US decision to recognise Jerusalem as Israel's capital. And he's currently serving the longest consecutive term of any Israeli Prime Minister.

But all of that could be undone by police, who have been investigating two corruption cases involving Mr Netanyahu for the last year.

The results of the investigation are expected within the coming weeks.

"It's hard to say when we've reached that red line, that we're now in crisis mode," Anshel Pfeffer, writer with the newspaper Haaretz, said.

"When you listen to Netanyahu's speeches, and you see the way his proxies in the media are reacting, they certainly feel it's serious."

Mr Netanyahu has called the corruption investigation "fake news," and earlier this year tweeted a two-word response to speculation he would be forced from office: "Wont' happen".

Police are investigating two corruption cases focused on the Israeli Prime Minister.

The first involves Australian businessman James Packer, and another Israeli billionaire.

Mr Netanyahu is alleged to have taken tens of thousands of dollars' worth of gifts from the two businessmen — including champagne, flights, and hotel rooms.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 9 minutes 35 seconds 9 m James Packer reportedly gave lavish gifts to Israeli Prime Minister Benjamin Netanyahu and his family.

He has acknowledged receiving the gifts but said he did nothing in return.

Police are trying to determine whether these constitute bribes, since Mr Packer is reportedly seeking Israeli residency status for tax purposes.

The second case involves allegations Mr Netanyahu made a deal with a newspaper publisher to pass a law that would harm a rival paper, in exchange for favourable coverage.

No precedent of serving PM 'being on the stand as a suspect'

Mr Netanyahu has confidently predicted he will not be charged. But if he is, it could threaten his hold on power.

"There's no precedent of a serving prime minister being on the stand as a suspect in a criminal case," Pfeffer said.

"If that happens, Netanyahu will have to deal with a lot of pressure, both to resign and the pressure to go to elections."

A previous Israeli prime minister, Ehud Olmert, also faced a police corruption probe.

He resigned before he was charged. He was convicted and eventually served 16 months in prison.

But it is far too early to be writing Mr Netanyahu's political obituary, according to The Times of Israel editor David Horovitz.

"We don't really know for certain how grave these allegations are," Mr Horovitz said.

Even if Mr Netanyahu is charged, it is very possible he could weather the storm. That's because much of the Israeli public sees few other potential leaders that could rival him on the political landscape.

"He is … trusted as a leader who can keep this country safe," Mr Horovitz said.

"That's the key thing for Israelis. When they look around at the alternatives, they have not yet been convinced that somebody could do better at keeping this tiny country in this perilous region safe."

No-one, it seems, is prepared to count out one of Israel's great political survivors — yet.