The latest Newspoll (Australia's most reputable polling agency) has seen him fall further behind the Labor Party opposition, right at a time when a gaggle of by-elections are in the offing.
It also comes at a time when internally conservatives within the government are openly questioning the PMs judgment more generally.
As Turnbull flew from Vietnam to the Manila for Monday's ASEAN meeting
, the citizenship crisis that's prompted a string of sackings and resignations claimed another scalp.
On the weekend, Liberal MP, John Alexander, quit parliament forcing a by-election in his seat, on concerns that he might be a dual British citizen. The former tennis champion's Sydney metropolitan electorate is tough to hold, on a margin just under 8%. The by-election, which Alexander will recontest, will be held next month.
This follows another by-election, also set down for December, for the Nationals leader and former deputy prime minister Barnaby Joyce's seat of New England in regional New South Wales. Joyce was disqualified from holding office
due to his New Zealand heritage, though he's expected to win it back.
A host of senators from various parties have already fallen foul of Australia's constitutional rules, preventing members of parliament (MPs) and senators holding dual citizenship. Section 44 of the Constitution is quite clear that members of the federal parliament cannot have an allegiance to a foreign power. MPs have been struck out on this provision before, but not on the scale we've seen during the life of this parliament.
The government tried to petition the High Court to take an activist interpretation of the law and allow dual citizenship when MPs didn't know they held, or didn't apply to hold, such status. But the court ruled against the government unanimously.
The assumption now is that there may be a number of other MPs and senators who are serving in violation of the Constitution. Two weeks ago, the President of the Senate Stephen Parry sensationally resigned
, having hidden his suspicion that he held UK citizenship.
On Monday, after a week of negotiation, the opposition and the government agreed to a process for evaluating who might still be under a citizenship cloud within the parliament. Both parties have given members of the country's parliament until December 1 to disclose any dual nationalities and steps to renounce them.
It's a voluntary system which has the appearance of a detente between the parties as its goal, rather than getting to the bottom of who may or may not really be ineligible.
The problem for Turnbull is that his majority is wafer thin. At the 2016 election his government was returned with just 76 of the 150 seats in the lower house. It represents a one-seat majority, which means if his government loses any seats at by-elections forced by the citizenship chaos, the Coalition might be forced to a general election.
Returning to the latest polling, with the Coalition trailing 45-55% on the two-party vote, that's the last thing Turnbull wants. Hopes of a positive lift in the polls leading into the summer recess, off the back of the expected passage of same-sex marriage laws after years of toxic debate, have been dashed by events out of the PM's control.
Adding to Turnbull's woes are the latest personal numbers in the poll. They revealed that Australian Foreign Minister and long term Liberal Party deputy leader Julie Bishop is now more popular than Turnbull, and by a significant margin. Previously, despite poor party polling, Turnbull's personal favorability numbers protected him somewhat from his critics who would like to see a challenge to his leadership.
Forty percent of voters favor Bishop as leader compared to just 27% for Turnbull. This is fueling speculation that Turnbull won't survive the year or, if he does, a leadership showdown early next year might be in the offing. Bishop tried to shut down speculation of a leadership challenge by saying Monday that Turnbull would lead the party at the next election (or something along those lines).
Labor doesn't appear to be immune from the citizenship chaos either. A number of its MPs have questionable credentials when it comes to having renounced their dual citizenship before the last election. But even if Labor also loses MPs to by-elections, the odds are that, with the polls where they currently are, Labor seats would be retained with swings to the opposition, cementing the view that Turnbull is in trouble.
The senate is sitting this week, but when the House of Representatives returns for sitting in two weeks' time the opposition will test Turnbull on the floor of the chamber. His government is already two MPs down, meaning that there is a risk that the opposition, in conjunction with the crossbenchers, could succeed in forcing through legislation the government doesn't want, or even a no confidence motion sparking an early election.
Australia has become the Italy of the south in recent years -- six prime ministerships since 2007. Turnbull risks falling victim to this phenomenon, courtesy of the citizenship saga and enduring poor polls.