Pause here before we rush headlong into the turbulent future. Stop and inhale last week’s rare political triumph, revel in the sunshine of cheery optimism. It was a precious but unfamiliar sensation when life on the progressive side of politics in Britain is so often a litany of hopes dashed and disappointments.

Andy Burnham’s comprehensive victory in the Makerfield byelection, surpassing expectations, was a precious moment. He demolished £5m-Nigel Farage’s party of loathsome Reformers, whose every election candidate seems more repugnant than the last. Hostile hard-right politics in Britain needs defeating time and time again, every time nativists and hate-stirrers – from Enoch Powell to the BNP – erupt in our politics.

No one but Andy Burnham could have stamped out Reform in a part of Greater Manchester where it had just won every council seat only last month. And how heartening it was that not just Liberal Democrat and Green voters but Makerfield Tories too lent him their votes because they understood that keeping out Reform mattered most: forget flag waving, that’s what patriotism looks like. I will relish Makerfield alongside other rare dates; I delivered leaflets before I could vote in the 1964 election which put and end to what Harold Wilson called “13 years of Tory misrule”. Remember where you were the night of Labour’s great 1997 win after 18 wilderness years? Obama night was best of all. I will relish Makerfield alongside those other rare dates.

As Keir Starmer drafts his resignation speech – expected to be delivered on Monday – let’s also recall how he vanquished 14 years of Conservative rule, a triumph after the Jeremy Corbyn wipeout of 2019. But, in truth, Labour’s 2024 general election victory was a freak landslide, won on a paltry 33.7% of the vote. It never felt like a surge of public enthusiasm. The Starmer government struggled from its early days to inspire affection. Why? His speech in the Downing Street garden spoke about a “painful” budget to come as Rachel Reeves announced there was a £22bn black hole in the Treasury. It set a glum tone. Honesty doesn’t always pay.

The first 100 days saw much good done: rail nationalised, bills introduced to improve renters’ and workers’ rights, bus services freed up to local control, free school breakfast clubs rolled out, good public-sector pay deals, and restrictions on onshore windfarms ended. But so much of what his government accomplished was visible only to political obsessives who were aware of announcements on Great British Energy, the national wealth fund, liberalised planning laws for housing and the new border security command.

But what did catch the public eye, just a month into power, was that unexpected cut in pensioners’ winter fuel allowance: cue stock images in the minds of voters of cold old folk wrapped in blankets. If only they had abolished the two-child benefit cap the same day, an old-to-young swap would have resonated well. The other eye-catcher was making farmers pay inheritance tax on a level a bit closer to everyone else’s: cue picturesque tractor protests in Whitehall.

Starmer always lacked a sense of political theatre, but reports of free suits, glasses and gig tickets offered all too vivid imagery, deeply damaging a new, clean regime. It may have been a drop in the ocean compared with the big money political scandals common on the right, but it stuck. Time and again on doorsteps at Makerfield and in recent byelections when I heard people say they “hated” him, those were the only reasons they could think of. No good telling them someone like me getting a winter fuel allowance was absurd or that farmers’ land is pretty valuable: their firmly fixed image was Starmer punishing Old Mother Hubbard and Old MacDonald.

In other words, the vital lesson for Andy Burnham is this: good first impressions are everything. He could look for inspiration to the remarkable Blair/Brown first 100 days in 1997: a windfall levy of £5bn on underpriced privatised utilities, VAT cuts, stamp duty raised on expensive properties, the first ever minimum wage set in motion, child benefit raised – and yes, that winter fuel allowance created.

Every early gesture will brand his future. But his portfolio of promises includes plenty of beacons to illuminate the Burnham way, immediately and memorably. He should start with first steps on easing the cost of living with his reported plan to freeze rents for a year for the roughly 20% of the country who are private-sector tenants.

His other reported ideas should be up and running as soon as possible. That includes capping bus fares at £2, cutting energy bills by shifting green levies on to general taxation, and cutting business rates for pubs and small shops. Equalising tax rates for income tax and capital gains, as Wes Streeting advocates, would more than cover these, along with blocking that private equity tax loophole – something Starmer promised but didn’t fully deliver. Repossess the failing water companies, Thames Water first, and declare his long-term intent to take back control of the National Grid.

Radicalism can also be cost-free. Burnham (perhaps rashly) promises a breath of fresh air in parliament by relaxing the government whip, freeing his MPs to speak their mind more often. One benefit would be suffering fewer excruciating ministers sent out miserably to read official “lines” to take. Next, it’s time to clean up politics: take dirty money out of Westminster with a strict cap on all political donations.

He is expected to send up flares signalling the start of his promised constitutional reform. Begin the complex devolution route to “Manchesterise” local mayors, with powers to tax and spend, and oversight of schools and health. Longtime backer of fairer elections, Burnham should appoint his promised national commission on proportional representation now: that secures tactical voting support from all progressive parties eager to see it happen.

It’s a lavish tasting menu, yet it’s only for starters. No one can complain he doesn’t have substantial policies. Add in a warmer EU embrace on this Brexit anniversary and chillier caution in coping with the White House. All of this would tell a good story about what Labour is, who it’s for, what it can do. That sense of purpose and direction is all that can keep him motoring ahead when confronted by a monstrous intray of wants and needs, with too little money. Hope is the word and he’s good at it.

But choosing his chancellor will be his most perilously emblematic first act. The hostile press – alongside Unite’s Sharon Graham, never one to miss the chance of throwing spanners in Labour’s works – are trying to poison Ed Miliband’s chances, though he is the more serious economist and the most experienced at dealing with rigid Treasury obstructionism. The exchequer could end up being Wes Streeting’s consolation for not standing, but that could create a narrative of Blair-Brown-esque friction. Keeping Rachel Reeves would steady the markets, says her team.

As for the process of how the next PM is selected – who needs a long, politically damaging leadership contest when the result was written in Makerfield? Meanwhile, let Starmer go with good grace. His political tragedy is that he leaves a strong legacy of much good done, as Labour always does, from universal nursery places to falling NHS waiting lists. As for the future, as the only popular leading politician, Burnham may buck the current terrible trend: each of our last four prime ministers has been the most unpopular ever in their time. Keep chanting the mantra – hope and change, hope and change, hope and change.

• Polly Toynbee is a Guardian columnist