The Andrews Labor government has been kicked hard in the guts once more by its greatest nemesis: the Victorian Labor Party.

For the government, Thursday was supposed to be all about turning the screws on Opposition Leader Matthew Guy and ruthlessly exploiting his record as planning minister over the contentious Fishermans Bend precinct.

Instead Labor was plunged into crisis by an (alleged) physical scrap between ministers and an ex-minister.

In the state Parliament. Good luck trying to keep that quiet.

Labor factional powerbroker Adem Somyurek vehemently denies threatening tourism minister John Eren with a butter knife during a heated dispute, but parliamentary authorities will now investigate the claims.

Nine months out from an election. Do these MPs even want to win?

You couldn’t script a better example of the problems that have dogged Andrews since he won government in 2014.

There’s a long and complicated tale behind Wednesday night's boilover in Parliament’s swank members-only dining room between Somyurek and Eren.

But the back story is less important than the broader plot, that pretty much all of Andrews’ problems since 2014 have been the result of Labor infighting, leaking, political takedowns and ‘‘drive-bys’’.

The friendly fire has been much more damaging than anything the Guy-led opposition has managed.

And Somyurek has featured time and again, sometimes in the spotlight, sometimes behind the scenes.

It’s not like there haven’t been lessons to learn: Andrews and Labor were pretty lucky to win government from a Coalition outfit that fell apart under a series of hammer blows from its own ranks.

The - ahem -‘‘maverick’’ MP, from Melbourne’s south-east, Geoff Shaw, and the chaos he was able to generate around him, were major factors in the former Coalition government's descent from relative strength to joke status in voters’ minds.

Somyurek, sacked from the ministry amid a bullying scandal in 2015, is no Geoff Shaw.

But he still might do to Andrews what Shaw did to Baillieu and Napthine, while all the while protesting that he's a "force for stability".

It might be already too late for the Premier to escape the fate of his predecessors.

Somyurek denies the allegations against him.

His friends who were there that night back him up and say this is a factional stitch-up.

But voters, looking for a competent outfit to govern their state, are unlikely to care about any of that.

Nor does it help that the Premier will catch a plane to the US on Friday morning and won't be around for several days to provide the leadership his party so badly needs.

The Labor government can put together a case in November that it hasn’t performed all that badly.

But the Labor Party has been horrible, and if Andrews and co want to win another term, they must first overcome their own worst enemy.