When cartoonists draw the Labour leader Sir Keir Starmer they like to zero in on his ruddy cheeks, and for good reason. Like some sort of traffic light system, the colour in his face goes up or down depending on how under pressure he feels.

Yesterday, campaigning in the Rutherglen and Hamilton West by-election, the lights seemed stuck on red. Sir Keir did a lot of smiling but at the same time he seemed wary.

It is the default position for many visiting leaders, including Rishi Sunak. They are not cautious around Scots in general, but they do think our media require watching closely. Little did Tony Blair know when he called Scottish reporters unreconstructed something-or-others, that all these years on a new generation would be wearing the badge with pride.

The task for Labour yesterday was a familiar one: show that the party is one big happy family. Can’t slip a Rizla paper between London and Scotland, a partnership of equals, none of your branch office and headquarters here. Or as Sir Keir put it when asked about his bond with Scottish Labour leader Anas Sarwar, “Anas and I have got a very, very strong working relationship, so anybody who is trying to find division is going to have a very, very long search.”

The search, in fact, was very, very quick, if indeed much digging was required at all. The two sides were obviously at odds over the two-child benefits cap (Sir Keir would not scrap), and gender recognition reform (Scottish Labour backed demedicalisation; Sir Keir, after a shaky start, is all for talking anatomy).

READ MORE: Starmer on scrapping benefits rule

This is more than a case of “potato/potatoh, tomato/tomahto”. The differences on gender reform are not quite as critical as they once might have been, although the Conservatives will still use the division to brand Labour as hopelessly woke or unable to make up its mind.

But not scrapping the two-child benefit cap, that is a whole different kettle of fundamentals. Mr Sarwar has said he would “press any incoming UK Labour government to move as fast as they can within our fiscal rules to remove this heinous policy”.

What a guddle the Scottish Labour leader has got himself into there. “As fast as they can”, “within our fiscal rules”. One would think he was asking for a new carpet for the branch office, not demanding something that could lift 250,000 children out of poverty.

In not committing a Labour Government to scrap the cap, Sir Keir is standing on the side of George Osborne, Mr Austerity himself, rather than his own MPs and the wider party. That is a shameful place for any Labour leader to be.

Yesterday in Rutherglen he seemed prepared to shift on this, saying there was “nothing to say an incoming Labour government can’t make sure that the policies we’ve got can operate more fairly. I think you’d expect that from a Labour government and you’ll get that from a Labour government”.

READ MORE Sturgeon arrest an issue in by-election says Sarwar

It was not a commitment to scrap the cap and accompanying “rape clause”, but it was a step back from the tone and language he has been using recently. When he appeared on stage with Tony Blair at a conference organised by the former Prime Minister’s think tank, Sir Keir defended his stance, saying it was just the beginning of the “tough choices” and “really ruthless” decisions that have to be made if Labour was to stand a chance of forming the next UK government.

The party has heard it all before, and from Mr Blair in particular. This year’s backing of the benefits cap, or some other hitherto unthinkable stance, is yesteryear’s scrapping of Clause 4. Sure, it sticks in the craw, but what a big picture message it sends.

The ham actor in Mr Blair liked to indulge in such posturing. One minute he was the macho man who had to get his own way, the next a victim of others’ inaction. The scars he bore on his back from trying to reform public services.

What a remarkable sight the Blair-Starmer combo made. Both wearing suits, white shirts, no ties, they looked like a couple of international executives shooting the breeze in some luxury airport lounge (they’re very popular apparently - the lounges, not the double act).

At one point this would have been considered an unwise move for Sir Keir, but he clearly thinks his opposition on Iraq, among other things, has put enough air miles between himself and the former Prime Minister. It will not be enough of a distance for some. You certainly cannot imagine a similar event happening in Scotland, where Mr Blair remains a controversial figure. One would describe him as Marmite, but a lot of people actually like Marmite.

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The “in conversation” session in London went so well, indeed, it fed speculation about what role Blair might play in any election campaign and in a future Starmer government. According to one “senior Labour official” quoted in a Times piece, “Our working assumption is that half of the Blair Institute will be flooding into Number 10 … once we’ve won.” And if one former Labour Prime Minister wants to have his say, what is the betting Gordon Brown won’t be far behind, if he’s not already in there?

Opposition parties are in two minds about being presented as governments in waiting. There is a risk of seeming complacent, but also a fear of not being seen as ready.

Sir Keir has a bigger problem on his hands, however, than which former PM will be inviting himself round for tea. It is a problem that has been there for a while, and it was evident in his trip to Scotland. For all his eagerness to serve, he is not close enough to sealing a deal with the electorate that will see him safely into government. North and south of the Border, voters have made plain their dissatisfaction with the status quo. They are against the Tories, and increasingly the SNP, but that does not mean they are for Sir Keir Starmer’s Labour.

Sir Keir was right when he spoke of the public being disillusioned with politics and needing something, someone, to believe in. On the evidence of this week he has a lot more to do before he can count on winning Scotland back.