Politicians are often criticised for empty rhetoric, but Sir Keir Starmer was right when he told activists in Swindon on Thursday, “these [local] elections matter”.

That’s because the May poll will be both the first big ballot box test for Rishi Sunak, and will give a sense of whether the momentum Sir Keir is showing in national polling translates into actual votes.

So there’s a lot at stake for both sides. As Sir Keir Starmer told me on a walkabout in Swindon: “I’m measuring this on the road to the next general election and I want to see the Labour Party making real progress.”

And it is a key staging post for Starmer’s Labour. The party will need to show it is the main beneficiary of lost Tory votes and that means big wins.

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If the Conservatives lose 500 of the 8,000 seats up for grabs across England, it would be the first time in over two decades that the Tories were not the biggest local party in England – a huge symbolic blow.

But Labour needs to do a lot more than that to prove they are on course for a general election victory.

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A net gain of 700 seats would mean Starmer’s Labour is still underperforming current polling. That sort of win would equate to a national equivalent vote share of around 37%.

To put that into context, in the 1995 locals ahead of the 1997 Labour landslide, Tony Blair achieved 47%.

So a net gain of more than 1,000 in these elections would be significant for Labour – a big success

Sir Keir refuses to put a number on what success would look like, but does say he “wants to get as many of those 1,000 seats as [he] can”, adding: “These local elections are very, very important to us.”

And part of that pathway for Sir Keir is trying to prove to the public that Labour has changed under his leadership.

‘Ruthless’

His clearest signal of this, beyond the patriotic speeches in front of Union Jacks, was Labour’s decision last week to bar Jeremy Corbyn standing as an MP in the next general election.

Three years ago, Sir Keir described Mr Corbyn as a “friend” – now he’s expelled him as an MP.

“I’m prepared to be ruthless to ensure we have a Labour government,” he tells me, unapologetic over a decision which Mr Corbyn has described as a “shameful attack on democracy”.

“There’s one person that’s responsible for the fact that Jeremy Corbyn will not be a candidate at the next general election and that’s Jeremy Corbyn,” said Sir Keir.

“I have been ruthless in the change in the Labour Party. I do not apologise for that because what matters most to me is that the change that millions of people desperately need across out country comes about.”

But like voters I’ve spoken to in the past few weeks in High Wycombe in Buckinghamshire, Pendle in Lancashire and now Swindon, the jury is still out on Sir Keir, with voters unsure about what he stands for.

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Sky News asked Jeremy Corbyn whether he’s thinking of standing as an independent MP

Labour may be way out ahead of the Conservatives in the polls, propelled by the own goals of the Johnson and Truss administrations, but what the party lacks is something crucial which Tony Blair had – a sense of excitement and a leader with huge personal appeal.

When I put that to Sir Keir, his only answer is that elections like these give him the opportunity to get around the country to make the case.

That Sir Keir hasn’t nailed it with voters is one of the Conservatives’ biggest hopes in turning around their fortunes in a general election.

If voters’ are unsure about the Labour leader, and his rival Mr Sunak can show competence and economic improvement as the country goes to the polls in a general election, might they stick with Sunak?

If that’s the Conservative hope, the reality for May’s local elections is that Labour will give the government a bloody nose.

Back at base in Downing Street there are expectations that the results will hurt.

“It’s not going to be good,” one senior figure told me the other day.

‘Big win needed’

There is some consolation that the King’s Coronation on 6 May will mean the painful post-election coverage will at least be short-lived.

But even if attention quickly shifts away from the results, these local elections will set the tenor for a political year that already feels like the beginning of the long campaign to what could prove a seismic general election for the country should power pass from the Conservatives to Labour.

Labour wins in Swindon, in parts of the Tees Valley, such as Middlesbrough or in Hartlepool, will be important, as will progress in the Midlands – Dudley, Walsall – and North East Derbyshire, where councils and constituencies have been surrendered to the Tories in recent years.

Will 2024 turn out to be Labour’s 1997 of 1992, the landslide or the narrow defeat?

To keep momentum for the former, Sir Keir needs to win big in May.