As long as Gerry Adams remains leader of Sinn Féin, his past will haunt him, and act as a drag on his party's fortunes.

No, it’s not the past you are thinking of - even though his links to the IRA remain a deterrent for voters outside the party’s traditional support.

It’s the other past, namely the difficulties he has had over the years when it comes to grasping, and explaining, policy detail, especially on finance.

Ask Adams any question about the North or the peace process or the tragic by-products of violence and terror and he will not be bested. As well as having encyclopaedic knowledge and a clear strategy, he also a passion - and a “feel” - for it. It’s not surprising. This has dominated his life.

But south of the border there are a whole different set of issues and some bring the Sinn Féin leader far outside his comfort zone. The finer details of policy, especially finance policy, seem to confound him, making him sound ponderous.

In the first debate, Joan Burton chided Sinn Féin for its fuzzy economics. The fuzziness extends to the leaders's grasp of figures. It's not just the information gap, you sense he does not have a "feel" for it.

It's not a new difficulty for Adams by any means. In the 2007 election, there was a second-tier leaders debate, featuring the four leaders of the then smaller parties: Pat Rabbitte of Labour; Trevor Sargent of the Greens; Michael McDowell of the Progressive Democrats; and Adams.

That week Adams had fronted his party's conference on finance policies, which Sinn Féin economic advisor Joanne Spain had prepared. Adams faltered over figures, confused the media present, and seemed confused himself.

You would have though by the time he hit the live debate on RTÉ he would have repaired his hand. But he again stumbled through the finance figures.

It prompted a scathing and painfully patronising outburst from McDowell from which there was no comeback: “Gerry, you know absolutely no basic figures or basic facts about [FINANCE]. Every time Mark [Little, the presenter] has asked you a question you’ve changed the subject to the peace process or the health service, because you just don’t know”.

Is Gerry Adams an asset or a liability for Sinn Féin?

He is both but probably more of an asset than the media acknowledges. There is an instant recognition factor - he is, in a way, a political TV celebrity. That is a factor with traditional Sinn Féin supporters - be they republican or blue collar. That constituency was served by Adams’ tour bus, that travelled throughout the country, mainly visiting core Sinn Féin areas.

The challenge for the party has been extending its appeal beyond those cohorts and overcoming people’s reservations about its violent past by presenting a modern face, biddable policies tailored for the south, and new faces untarnished by the past.

Because he is leader, Adams is the person who has straddled those two worlds, but not smoothly. He and Sinn Féin had a tremendous first week of the campaign. The party was able to force the Government parties to concede on the extent of the “fiscal space”.

It also stood out as the only party opposing the abolition of the Universal Social Charge (USC). Indeed Fine Gael had lambasted Sinn Féin for wanting a third rate of tax for those earning over €100,000. Sinn Féin was able to hit back effectively when Fine Gael said there would be a clawback of 5 per cent tax for those earning over €100,000 when USC went.

It was a different tax entirely but Sinn Féin was able to portray it as Fine Gael doing more or less what it had already done. It worked. Fine Gael’s “corrective” measures were just too hard to explain.

Adams held his own in the first two leaders’ debates. He was faced with “stone-in-the-shoe” questions about Thomas “Slab” Murphy, his medical treatment in the US, and his IRA past. He dealt with them as he has dealt with them in the past.

His difficulties began with two media interviews last Thursday. The first was on RTÉ's Today with Sean O'Rourke where Adams showed he was no twinkletoes when it came to thinking on his feet about the economy.

O’Rourke put a basic proposition to him. Water charges cost €160 net for anyone who applies for the €100 grant. It’s a fact but Adams kept on insisting that the savings people would make from abolishing water charges would be the gross €260 figure. He could not acknowledge the net figure despite persistent questioning.

He spend an age trying unsuccessfully to explain his party’s third rate of tax for those earning over €100,000. When O’Rourke brought up an example that hardly merited sympathy of a civil servant earning €187,000, Adams did not see the yawning open goal in front of him.

Later that evening with Bryan Dobson on Six-One, Adams fared little better when dealing with high earners.

It’s arguable some voters who might have been edging towards Sinn Féin drew back after the interviews, on the basis that Adams had a credibility issue on economic management. The seed of a narrative (“not great on the sums”) had been sown that Thursday. It persevered through the final leaders debate, where he did not look convincing on details.

Sinn Féin’s support levels in polls always looked likely to drift a little but Adams’ difficulties may have had an additional impact. Strong first week. Poor second week. So-so third week. That has summed up his campaign.