Overall pattern is what matters in opinion polls

JUST how much faith should be placed in the opinion polls of recent days?

Certain parties and politicians are entitled to scoff at the notion that polls are accurate barometers of the public’s voting intentions.

For instance, according to opinion polls, Fine Gael’s Michael Creed was going to top the real poll in the Cork North West constituency in the last general election.

In fact, the polar opposite happened: he lost his seat.

The PDs, meanwhile, were supposed to face electoral wipe-out last time round.

Instead, they doubled their amount of seats in the Dáil from four to eight.

Now, this week, we are presented with a poll which suggests support for Fianna Fáil has surged five points to 41% in a little over a week.

The TNS MRBI poll, carried out for the Irish Times, suggests Fine Gael has dropped one point to 27%, Labour has fallen three points to 10%, and the PDs remain static on 2%.

So are these the figures the parties will actually realise on Thursday?

The answer is probably not. The numbers will be different. Crucially, however, the patterns indicated by this and other polls are likely to be accurate.

In 2002, for example, the equivalent MRBI poll afforded Fianna Fáil 45% when in fact the party received only 41.5% on polling day — a substantial difference given that 3.5% can mean a difference of several seats. Another poll, conducted by IMS for the Irish Independent, was even further off the mark, putting Fianna Fáil on 50%.

MRBI was a little closer in its measurement of Fine Gael’s support rating. Its poll said Fine Gael was on 21%; it achieved 22.5% on election day.

MRBI put Labour on 12%, when it received 10.8%. The poll placed the PDs on 2%; the party took 4% of the vote.

The numbers left something to be desired, then — support for Fianna Fáil several points overstated, support for the PDs understated by half.

But if looked at in terms of overall pattern, the poll was accurate.

The poll numbers, for example, suggested Fianna Fáil and the PDs would be returned to government with 47% of the vote between them, compared with just 33% for Fine Gael and Labour. In the end, that was almost exactly what happened — Fianna Fáil and the PDs took 45.5% on the day while Fine Gael and Labour took 33.3%.

Therefore, this week, the parties will look at the poll numbers and adopt some healthy scepticism. Fianna Fáil, for example, will not dare believe its support is actually as high as 41% — party strategists believe 39% is more accurate. Conversely, Labour will tell itself that its support isn’t as low as 10%. And so on.

But it’s the overall pattern that matters. The poll suggests Fianna Fáil is back in the races, and together with the PDs, would have 43% of the vote on the day. The alternative government of Fine Gael, Labour and the Greens would also have 43% between them.

For months now, seasoned political observers have predicted the election will be a very tight one, and that a Fianna Fáil-Labour alliance might be the only one with sufficient numbers to form a clear majority. The polls mightn’t nail the numbers, but the pattern certainly seems about right.