There is a lot of political meteorology going on in Westminster at the moment. MPs are acutely sensitive to what they see as seasonal changes in the way they are portrayed by the media. They aren’t wrong to detect that press coverage tends to shift in weather patterns, with a prevailing wind blowing at the backs of some candidates and hard in the faces of others.

Mostly, those trends track opinion polls and perceptions of one party leader’s performance. But they can also become self-sustaining – feedback loops of positive or negative coverage. Besides, journalists hunt in packs. Once a pattern for coverage is established it can fix a distorting lens on the news agenda, through which every detail is filtered. Thus, for example, when Gordon Brown was enjoying his short honeymoon as Prime Minister – respected for seriousness of purpose and an earnest demeanour – David Cameron was going through one of those periods where a lack of policy heft was drawing criticism.

It was summer and images of the Conservative leader in shorts on the beach seemed to suggest a boyish unreadiness for office, as compared to Brown’s besuited seriousness. Fast forward a year. Brown’s leadership was in crisis and Cameron was looking more like the next Prime Minister. Suddenly the same holiday snaps made the Tory leader look like an ordinary guy, at ease with himself and the country; his Labour counterpart was robotic and aloof. The people had not changed but in journalistic terms, the story was different.

At the start of this year, Ed Miliband looked weak. David Cameron was enjoying a poll bounce after his (non) veto of a European treaty. Labour MPs were anxious and chattering nervously about the inadequacy of their leadership. The whole opposition project looked shaky and everything Miliband did seemed to feed into that narrative. A misspelled tweet referring to an 80s quiz programme as “blackbusters” instead of “blockbusters” was treated as an enormous gaffe, practically rocking the foundations of the Labour party.

Then came a Labour spring. George Osborne’s budget failed. It got tangled up in a whole bunch of bungled policy presentations and botched media performances now known collectively as the “omnishambles”. Suddenly, Miliband was to be taken seriously as a potential Prime Minister. Divisions in the coalition were all potentially fatal; the Tory leadership was in question. Everything Cameron did has subsequently been shone through the new jaundiced lens. Take, for example, reports that the Prime Minister sipped wine while administering his recent reshuffle – a fairly unremarkable detail in most respects. Except it was treated as proof that Cameron is heartless and arrogant. He quaffed claret and failed to offer a glass to his brutally despatched underlings, like a drunken lord dismissing his downtrodden staff.  Two years ago it would have been evidence of what a supremely confident and relaxed man he is, effortlessly carrying out the duties of high office when his predecessor was surly and uptight. Cameron the natural.

Obviously these changes in presentation are informed by choices the politicians themselves make. Mistakes and successes are amplified; confidence breeds good coverage, insecurity invites a kicking. The budget provoked bad headlines because it was not, by most standards, a good budget. Miliband got a fairer hearing because he held his nerve, made some judgement calls and said things that forced his party and the media to pay closer attention.

Nonetheless, the press pack gets bored with any particular story and impatient for a new one. Many Westminster fingers are currently being held aloft, sensing the wind changing. So Miliband could be Prime Minister? Really? So what’s he really on about? And what’s all this about friction with Ed Balls? That’s the story, surely. And wait a minute! Could those be green shoots of economic recovery just visible puncturing the arid soil? A bit of growth and surely the Tories can start closing the gap in the polls. Of course they’d be behind mid-term when forced to take unpopular decisions, but compare the personal ratings of Miliband and Cameron. When it comes down to it, the nation has a clear favourite to be Prime Minister – this could be the colour of political coverage for the new season.

Everything depends, of course, on whether the leaders and their parties can get through party conferences without any mishaps. I wouldn’t want to suggest that the whole direction of politics is dictated by mood swings of editors, reporters and commentators with short attention spans. But I detect from Labour and Tories alike (in the form of anxiety on the former side; hope on the latter) that a different weather system is drifting in.

On the Conservative side, much depends on whether or not a huge Boris Johnson-shaped cloud rains on Cameron’s conference parade. There is clearly concern in Downing Street about the PM being upstaged.

For Labour, concern is centred on the leader’s speech. Last year’s intervention from the podium got mixed reviews to say the least. Only later, when the weather had changed, did it become conventional wisdom to see Miliband’s disquisition on predatory and productive modes of capitalism as a perceptive, agenda-setting insight. Now there is pressure on the leader to advance his position with a more concrete – and more pithily phrased offer; something that starts to sketch the outlines of a winnable campaign. The advice from one senior Labour figure close to Miliband, not terribly helpful but certainly true and applicable to Cameron too, and Nick Clegg for that matter: “Just don’t screw it up.”