We may still be in the midst of this year's general election campaign, but the opening shots of next year's Holyrood election have already been fired by the man who has everything to gain or lose when the 2016 election happens: the Scottish Labour leader Jim Murphy.

In an interview with The Herald, Mr Murphy makes it clear that if Labour wins at Westminster next month and Ed Miliband becomes Prime Minister, Scottish Labour will seek to implement key parts of its manifesto at Holyrood before the 2016 election.

The idea is to force a series of votes at Holyrood on Labour's promises such as employing 1000 extra nurses for the Scottish NHS and an extra £200million for cancer care. Mr Murphy says the aim would be to hold the SNP's feet to the fire before the election next year, but it is really a challenge to the SNP to vote against more doctors and nurses.

It is by no means certain that Mr Murphy's strategy would work. If Labour wins the general election, and if it delivers on the extra £800million promised for Scotland, paid for partly by a mansion tax and a tax on bankers' bonuses, the danger is that Nicola Sturgeon will simply spend the money and take all the credit. Mr Murphy hopes instead that by forcing votes on how the £800million is spent, he can put the SNP into an awkward position and also draw a line between the nationalists and Labour, with Labour painted as the pro-NHS, progressive party.

The reason the Scottish Labour leader wants to do all this before the 2016 Holyrood election is that he is desperate to reverse, or slow, the SNP's extraordinary momentum. The concern for Labour is that, if the SNP has a good general election, as seems almost certain, the success could roll on to 2016 and deliver them another majority Scottish Government.

What will make it difficult for Mr Murphy to change Labour's fortunes ahead of 2016 is the fact that there has been a profound change in the way Scottish voters behave in elections. The death yesterday of Labour's Tom McCabe, the very first MSP, is a reminder of what the early Holyrood elections were like: turn-out was relatively low and many voters would behave in a different way to the way they did at general elections. The referendum has changed that: now, Nicola Sturgeon is playing a central role in the general election even though she is not an MP, and many voters appear to be starting a habit of voting the same way at Holyrood and at general elections - that is, SNP.

Another issue for Mr Murphy is that the £800million which he says is coming Scotland's way is by no means guaranteed. The shadow chancellor Ed Balls has promised it will happen, paid for by new taxes such as the tax on mansions and a levy on tobacco firms, but Mr Balls has not set out his spending plans year by year and, unless the economy takes off, he has made it plain that Scotland will not escape any cuts.

We can be sure the nationalists would make the most of that and, even if the £800million is forthcoming in 2015/16, they will suggest it is offset by cuts to the Holyrood budget. In the circumstances, Mr Murphy may still go ahead with his strategy, and dare the SNP to vote against him, in an attempt to establish Scottish Labour as genuinely radical and the SNP as quasi-radical. How the SNP respond to that strategy will set the tone for the 2016 Holyrood election. The bad news for those already suffering general election fatigue is that that 2016 campaign has already started.