THE sap is rising. For most of the last decade, spring has meant an election of some sort - local, Holyrood, Westminster or European. But this year political body clocks have been disappointed, at least in Scotland. There are local elections in England next month, but here that restless campaigning energy lacks an outlet.

Perhaps it explains this week’s turbulence among independence supporters, as they focus on the date of a second referendum and knock each other instead of doors.

The divisions highlight a very real dilemma for Nicola Sturgeon, to which there is no neat solution.

They also suggest the long-foretold battle between the SNP’s impatient membership and its unhurried leadership is finally kicking off.

The First Minister appears trapped. In last year’s snap election, she sought a “triple lock” mandate for a referendum. Her manifesto was clear. “If the SNP wins a majority of Scottish seats in this election, that would complete a triple lock, further reinforcing the democratic mandate which already exists.”

It added: “At the end of the Brexit process, when the final terms of the deal are known, it is right that Scotland should have a choice about our future.” Rather inconveniently, many in Ms Sturgeon’s party now expect her to stand by that.

However the First Minister has been in no rush to oblige. After her manifesto helped lose her 21 MPs and rallied folk to Ruth Davidson’s anti-referendum banner, Ms Sturgeon “reset” her plans and said she’d get back to the country with a “precise timescale” later this year.

That triple-lock mandate has been yellowing in a drawer ever since.

With some fearing it will never see the light of day again, there is now an anxious debate about whether there should be a fresh push for a referendum during this parliament. “Use it or lose it,” goes the plea.

Some old hands, including SNP MP Pete Wishart and former deputy SNP leader Jim Sillars, urge caution. Without clear public support for independence based on a refreshed prospectus, the SNP should be pragmatic and wait, they say. A second defeat would be disastrous.

But there is also a growing call for action. Blogger James Kelly argues Ms Sturgeon is honour bound to press ahead with the mandate, and that if she doesn’t before 2021 she may not get another chance, as only a small dip in SNP fortunes would see a Unionist majority at Holyrood.

Stuart Campbell, of Wings Over Scotland, made the same point. “The clock is ticking on the mandate... Independence won’t be easy to win in 2019 or 2020, but it’ll be a hundred times harder in 2022 or 2025 - even if by some miracle there’s still a Holyrood majority [for independence].” The shrill note of panic was unmistakable.

SNP MP Angus Brendan MacNeil said he wanted a referendum held within 18 months. Chris McEleny, one of the three candidates in the SNP deputy leadership race, wants the same. He is trying to turn the contest into an internal referendum on holding a referendum. His pitch is that members should vote for him to tell Ms Sturgeon they want another crack at it next year, and the decision is bluntly not hers alone.

It means the issue is set to dominate the contest until the winner is named in June. Unless Mr McEleny is utterly crushed, it will then dog Ms Sturgeon all summer, piling on the pressure before her update to MSPs in the autumn.

Fed-up Yessers are also doing it for themselves, with the grassroots Yes DIY movement filling the void left by the SNP leadership by organising marches, conferences and workshops around the country.

Although such gung-ho events do not necessarily reflect the mixed mood in the SNP, they must surely prompt its members to ponder why their party is not similarly active or focused on its founding mission.

So what does Ms Sturgeon do? She knows her core policy is not popular enough right now, and defeat in a referendum means resignation. More realistically, she knows agitating for a referendum and being denied one by London could still cheese off enough voters to turn the 2021 election into a rout.

But this is, after all, more than a political question. It is an existential one. If the SNP isn’t about pushing for independence, what is it for? Leaving mandates in drawers?

Some say Ms Sturgeon is too cautious to go for it. This is plainly wrong because she has done it already. She called a referendum last year despite the polls. Her plan stalled, but she was ready to gamble.

Playing it long has its downsides too. It would inflame a large part of her party. Discipline would fray.

Running an even smaller minority government after 2021, checked by a pro-Union parliament, would be death by a thousand cuts.

Her government would be buried by its own record on health and education, and there would be no constitutional distractions.

There would be recriminations over that unused mandate. As members brooded on what might have been, Ms Sturgeon could go down in SNP history as the boss who flunked it. Leader for six years by 2021, she would face endless speculation about stepping down.

Mr Sillars said this week the SNP could not afford another glorious defeat. The alternative for Ms Sturgeon may be an exasperating, ignominious decline. She has six months to make the call.