Victoria's political landscape is being turned upside down. One Nation is on track to become the state's most popular party, with fresh polling showing Pauline Hanson's anti-establishment movement hitting 28 per cent primary support.

The latest Resolve Political Monitor, conducted across May and June, reveals a dramatic shift. One Nation's primary vote jumped from 20 per cent in the first survey to 28 per cent in the second — that's the strongest result for any party.

Labor and the Coalition are both stuck on 26 per cent. Labor dropped one point, the Coalition dropped three. One Nation gained three points overall.

Senior strategists from both major parties privately admit that if these numbers hold until the November election, Victoria will almost certainly end up with a hung parliament.

Premier Jacinta Allan is feeling the heat. Her leadership is already the subject of speculation ahead of a caucus meeting on Tuesday. While she hasn't suffered the kind of polling disaster that would trigger an immediate challenge, the outlook is grim.

Labor's primary vote actually improved right after the May state budget, which included cost-of-living measures like half-priced public transport and 20 per cent discounts on car registrations. But it slumped again in the most recent survey, coinciding with fresh leadership rumours.

Allan's supporters blame a destabilisation campaign by a small group of party figures inside and outside parliament. Her detractors see the numbers as proof that she's leading Labor to defeat.

Resolve founder Jim Reed put it bluntly: "One Nation is in the ascendancy, as they are everywhere right now. If they keep gaining votes as they are, the sky is the limit."

Reed said the mood reminded him of the final term of the long-serving Labor government in New South Wales before the 2011 election, when the party churned through leaders but couldn't avoid a thrashing. "It's an end-of-days feeling," he said.

The poll asked whether the Allan government deserves another term. Only one in four voters agreed. Even among Labor voters, 31 per cent said no. Among One Nation voters, just 4 per cent thought Labor deserved another four years.

Nearly half of all voters declared the two-party system was finished.

On the flip side, 46 per cent of respondents agreed the opposition led by Jess Wilson was capable of governing, while 35 per cent disagreed.

One Nation leader Pauline Hanson, a Queensland senator, hasn't yet named her Victorian leader. But speculation is swirling after Adam Giles — a former Northern Territory chief minister who now lives in Victoria and oversees some of Gina Rinehart's business interests — attended a One Nation fundraiser in South Melbourne last week.

Giles said over the weekend he isn't a member of One Nation, has "no intention of running" for parliament, and hasn't "got any plans" to join. But he didn't rule out a leadership role if approached. "I'd consider it," he said.

Hanson told Friday night's fundraiser that One Nation would be willing to partner the Victorian Coalition in government. Former Liberal premier Jeff Kennett has urged his party to embrace that idea. Opposition leader Jess Wilson, when asked over the weekend whether she'd work with One Nation, didn't say no.