It was Margaret Thatcher who famously declared: “The only poll that matters is the general election.”

And over the years, many more party leaders have wisely repeated her cautious advice when confronted with huge opinion poll leads.

The Labour lead according to the latest YouGov MRP mega poll isn’t just big, however. It’s massive: a 154-seat majority for Sir Keir Starmer.

Not that the Labour leader will be popping any champagne corks or dreaming of moving into 10 Downing Street just yet.

Despite months of solid double opinion poll leads of up to 20%, Sir Keir has imposed an iron discipline on his inner circle and shadow cabinet members about the danger of complacency.

But there will be quiet satisfaction among the Labour high command that this latest mega poll confirms that the feared drop in the party’s poll lead over the Tories isn’t happening yet.

In fact, this YouGov MRP poll suggests that Labour is heading for a bigger majority than predicted in the last mega survey, back in mid-January, which forecast a 120-seat majority for Labour.

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Another change from the mid-January poll is that the number of people polled is up from around 14,000 to nearly 19,000, a truly enormous sample.

But if Labour will be reassured by these findings, the Conservatives will be plunged into yet another bout of blood-letting, open civil war and attempts to oust Rishi Sunak.

OK, let’s look at the most optimistic scenario for Mr Sunak and the Tories: that there are many thousand “don’t knows”, that Reform UK has peaked, and the waverers will return to the Conservatives.

One big health warning on the YouGov MRP poll is that it asked voters how they would vote if the election was held tomorrow. Well, it’s not going to be held tomorrow and may not be for more than six months.

On his electioneering tour of northeast England this week, Mr Sunak said he wants to hold the election when people “feel that things are improving” and repeated that he is planning to go to the polls in the second half of this year.

“I’ve said repeatedly and clearly that my working assumption would be that we have a general election in the second half of the year,” he told BBC Radio Newcastle. “There has been no change to that.”

The 154-seat Labour majority in the new poll is edging towards the 179-seat majority won by Tony Blair in 1997, though well short of a 254-seat majority suggested in another MRP-style poll in mid-February.

Many of the new poll’s predictions will no doubt be queried by MPs and party officials who will study its every detail in the hours and days ahead.

For example, many in the Labour high command will argue that the prediction of 201 gains and 403 seats for Sir Keir is on the high side, given the Tories currently have a working majority of 53 in the Commons.

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The SNP will surely dispute the projection that they’re on course to lose 29 seats in Scotland, down to just 19. And 38 gains for Sir Ed Davey’s LibDems, giving them 49 seats, seems a little optimistic.

Polls like this, however, will intensify the debate among MPs about whether the next election will be like 1992, when Neil Kinnock’s Labour were confident of victory but John Major won by 21 seats, or the 1997 Blair landslide.

Unlike now, when the government wins most Commons votes these days with majorities of around 70, by 1997 Major’s majority had all but disappeared. So as Sir Keir regularly points out, this time “we have a mountain to climb”.

Mrs Thatcher was right to be sceptical about opinion polls. But Sir Keir can take comfort from the fact that this new poll suggests that Labour is on the right path as the party attempts to climb the mountain.

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