Stan Greenberg cares about Britain. An all-American pollster, a legend of the trade, who helped deliver the White House for Bill Clinton and went on to advise leading politicians, including Nelson Mandela. For Greenberg, Britain has always held a special place in his heart. He's had a home here since he first worked for Tony Blair in the 1990s, and he's never lost his love for the old country, or for the Labour Party to which he dedicated so much of his time to help it win (he's advised all the Labour leaders except Corbyn).

It's Greenberg’s love for Britain and Labour that has led him to produce his latest large-scale polling on the state of British politics.

He arrived in the UK at a time of great challenge for the government, with the populist right on the rise, Trump attacking the Middle East, and rebellion at home over the government's welfare plans. Yet Greenberg argues his work is about demonstrating the opportunity that the government has for change—a chance to reset and rethink its strategy.

"There's an opportunity for Starmer and the government to look at what our polling is showing and say we see this, we understand this. The reason I did this survey was to create this kind of opportunity for the government to succeed, but they can only succeed within this new polarised framework that it sets out."

This shift towards, or perhaps even a return to, polarised politics sits at the heart of what Greenberg argues in his polling. His latest analysis, which he shared at a special UCL Policy Lab briefing, reveals a tectonic shift in how voters perceive the parties. As Greenberg explains, it's a shift grounded in values, with these values shaped by that most totemic of political figures – Donald Trump.

"The return of Trump is creating one bloc that is open to liberal and left parties, and one bloc that is open to conservative and right-wing nationalist parties. And the data shows almost no willingness to vote for a party that's not in their bloc. Movement within each bloc, sure, but not across the bloc."

In short, voters may move within the conservative bloc between Reform and the Conservatives. Or within the left bloc – between the Greens, the Liberal Democrats, and Labour. Some may stay at home. But vanishingly few are choosing to move between the blocs.

This matters; it matters for conservative parties, who are pushed to unify the right, as it seems Nigel Farage is seeking to do under a Trump-tinged banner. But just as critically, it matters for the left and progressives. And Greenberg believes it's crucial if Sir Keir Starmer is to turn around his government.

"When you look at the data, it's so powerful and so self-evident. And I'm trying to understand how you can look at this data and not conclude that there's a progressive bloc."

I ask Greenberg how far he thinks this polarisation on key touchstone cultural issues goes. He doesn't hesitate: "Very." He stresses its capacity to dominate how voters view politics at the moment.

"It's just very powerful—the polarisation and the joining of partisanship and culture to create this party polarisation are so stark. We first saw it with Remain; we saw it in Brexit in that battle." But Greenberg believes Trump has revitalised it and allowed it to bleed into other issues such as net zero, trade and international relations.

For Sir Keir Starmer, this poses a particular challenge. Since Trump's election, Starmer has sought to be a 'bridge' between the US and Europe. As Greenberg is quick to say, there are genuine reasons for this, and his role as PM means he must have a working relationship with the man in the White House; yet it's increasingly toxic politics for the Labour Prime Minister.

This progressive bloc is seeking a politics that speaks in opposition to Trumpian rhetoric, and, Greenberg believes, embodies their values.

The government, Greenberg believes, is failing to unify its voting base because it's failing to respond to the increasing polarisation. And it wasn't just Trump's rhetoric towards Ukraine. It runs deep—due to Trump, but also because its attached itself to totemic matters around Europe, including standing up for democracy, the rule of law, and net zero. Very little can escape the framing.

The polarisation runs into economic questions: "Trump's main economic policy[is] trade, along with climate, which has become part of these divisions driven by Trump. "Net zero has become something that Trump and other conservatives are fighting against, because for them it means government control, not just of the fossil fuel industry, and so it became a cultural fight for them." As this shift has occurred, voters, Greenberg argues, are searching for their bloc, their opposition to global Trumpism.

We may want to live in an age of the middle ground and cross-cutting coalitions, but Greenberg argues the times and Donald Trump won't allow it.

And just as Trump has driven a need for a tribune of the left, the economic turmoil unleashed by the trade wars has only further intensified the concerns about the cost of living.

"The cost of living is consuming for people. People are making day-to-day decisions about how to manage their finances. They get that the Tories created it, but they still want Labour to act." He's been here before. Greenberg advised Clinton when the then-candidate Clinton made economic recovery and a focus on the American middle class the heart of his presidential campaign.

Greenberg is quick to make clear that Clinton was, like all successful politicians, driven by values. He believed in reducing poverty and increasing taxes (Clinton committed to creating a new tax band) to do it. For Greenberg, the question of who you are for and how you respect them is crucial.

"What you're doing needs to go beyond raising wages; you need to look at the wider social support and help people with the everyday costs." Greenberg's analysis comes at a time when growing numbers of experts are suggesting the need for tax rises, a growing demand for public services, a push for increases in defence spending, and a need to meet fiscal targets—all pointing to the seeming inevitability of changes to tax policy.

If they are to come, Greenberg is clear about the need to accompany them with a clear change of direction, setting out values rooted in a progressive bloc that can rally around 'their' government. This bloc, in part forged by Donald Trump, is seeking a rallying cry, it seems, and it must be for the Labour Party to lead it.

“When you cross that bridge of tax rises, a red line, you tell people about your story and why you are doing what you are doing. When that moment comes, and it seems to be coming, then you must set out the values that underpin it.”

For Greenberg, the hard data backs it. As he sets out so clearly in his polling, we are living in a new polarised era. He wants Labour to win, and he thinks that to do so they must unite the left, just as Farage works to unite the right.

Yet he also speaks of something deeper; for Greenberg, politics is a game of both head and heart.

"The world needs Britain to lead now, not to be so much anti-Trump, but to lead in this battle for democracy and to address the climate crisis and reduce income inequality for people. To have an economy that does grow for all—and it's that kind of social and economic outcome and values that are also linked to the outward views toward Europe."

This is a fight for democracy, and although voters see it as a fight for a better standard of living, the values that underpin it are no less profound. For Sir Keir Starmer and his government, Greenberg’s polling poses real questions for its direction. Greenberg is clear of the opportunity – unite the left and win in this new age of polarisation.

It was an old US Senator who once said, “ya gotta dance with the one that brought you.” If Greenberg is right, it may be time for Starmer to dance with the one who brought him.