THE sartorial trouble with male politicians is that they too often fail to make an effort.

There was David Cameron yesterday, rallying the faithful at a Conservative gathering in Perth, wearing the same dreary old lounge suit beloved of the male politico everywhere, when there were other, more pressing clothing choices he might have made.

The Prime Minister could, for example, have sported one of the new £19.99 kilts being sold by the supermarket chain Lidl. Off-the-peg austerity in action. How his Chancellor would have approved, and how Jack McConnell, the former First Minister and hitherto the most ridiculed kilt wearer in history, would have joined in the cheering at his crown being stolen.

If it would have seemed bizarre for Mr Cameron to venture north wearing Highland dress, then it would have been only slightly less X-Files than what he did - namely, wrap himself in the Saltire and tell Scots it was positively patriotic to vote No.

There was no actual Saltire around his shoulders, of course. Unlike Mrs Salmond, Ruth Davidson, the leader of the Scottish Conservatives, is not given to keeping a flag in her handbag alongside the house keys, some out-of-date Tesco Clubcard vouchers and a spanner.

It was an imaginary Saltire the PM was wearing as he spoke of "the silent majority" and how it was time for their voices to be heard. Yes folks, he quoted Nixon at us as well. Excuse me while I wield the smelling salts.

Never mind whether we would buy a used car from Dave, is Scotland in a mood to buy such a message from Mr Cameron?

It would seem so, given a YouGov poll this week that had No leading Yes by 61% to 39%. But that is one poll among many. To misquote Rupert Murdoch, pollsters were created to make weathermen look good.

Yet put this poll together with the PM's visit, and the message he feels able to bring with him, and it begins to look like the campaign is taking a significant turn. When an Eton-educated, Conservative Prime Minister can make such an appeal to Scottish patriotism and not be laughed out of town, then the Yes camp have a problem. A big, fat, defeat-sized problem.

This was not the first, and it will not be the last, campaign visit by the PM. Like the well-brought-up lad he is (Scots dad, remember), he arrived here in May bearing a promise of further devolution if there was a No vote.

It was a promise, please note, not a guarantee, but it was enough to bring about another shift in campaign momentum away from Yes and towards No.

Emboldened, the Prime Minister is now tackling what he sees as the real problem with the independence debate so far: it has been quiet out there on the pro-Union side, too quiet for Mr Cameron's liking, and he wants to "rouse" the "silent majority" into action.

You may have trouble identifying this silent majority. One part of it, according to the Prime Minister in the Commons on Wednesday, comprises business leaders too afraid to speak out. Some of us must have been hearing voices, then, when the founder of Barrhead Travel and the BP chief executive aired their doubts about independence. As for the rest of this "silent majority", surely every person in Scotland, and their dugs, have by now been contacted by a polling company, received literature through the door, read miles of coverage and watched endless heated debates on television. We have been vox popped to within an inch of our sanity, poked and prodded by psephologists, and banjoed by statistics at every turn. Whatever else we are, we are not an uninformed lot. Nor are we backwards in coming forwards. So what is Mr Cameron talking about?

His is a seductive message, one that seeks to divide the Scottish electorate into them and us. He spoke of "the noise of the Nationalist few" without specifying who they were. Did he mean Yes campaigners in general, Scottish Government ministers, or the howl-at-the-moon brigade on the internet? That was left hanging in favour of talking up the "silent majority" he held so dear.

This majority was made up of those "who feel happy being part of the UK … who don't want the risks of going it alone … who worry about what separation would mean for their children and grandchildren".

He might as well have added "who think motherhood and apple pie are not too shabby", so broad were his brush strokes.

Essentially, however, the picture he wanted to paint was clear. If you want a quiet life, and who in their right mind does not, then you too are part of the silent majority and should vote No. Like the slogan "No, thanks" it is a negative message cloaked in positivity. Join us in doing nothing. Go for change by opting for the status quo. When it comes to scaling the height of cheek, Mr Cameron has found himself an Everest and sprinted to the top.

He is able to do this for a variety of reasons. First, Mr Cameron is no mug when it comes to punting a political message.

He has not lost any of that PR man's slickness or brazenness. Secondly, the option of sticking with the status quo appeals to voters' basic instincts. Ask any financial institution how quick customers are to change. If we cannot say cheerio to a useless current account, what chances of leaving a Union of 300 years standing?

The third reason why Mr Cameron can head north with the message that it is patriotic to vote No is because the Yes campaign are leaving the field wide open for him to do so.

The smartest move ever made by the Yes campaign was to present itself as the underdog in this fight. Even though the Yes camp has plenty of cash to call on and all the trappings and privileges of government on its side, it was able to position itself as an outsider, the wiry challenger to a bloated, power-drunk Westminster. But now it is allowing Mr Cameron to reverse this, to claim that he speaks for the underdog, and what the underdog wishes to bark is No.

And what can Mr Salmond, with only a few months to go until the vote, now do about it? Particularly when the UK Government can continue to pull cash out of the hat, as it did yesterday when promising £500 million for infrastructure projects in Glasgow. (Who needs Christmas when you have a referendum on the go?)

It could be the result of a punishingly long campaign. It may be that the forces ranged against them are too powerful, persistent or skilful. Whatever it is, the Yes campaign is starting to look tired and lacking in direction.

This may only be the leadership, and the grass roots, of whom so much are expected, are raring to go. As we have seen from Wimbledon this week, the real underdogs here (and despite all they have going for them, that is still the Yes camp), might yet have their day. But what events in SW19 have also shown is that the old hands, be it in tennis or politics, do not give up that easily.