When the polls are flattering to you or your party, you are in danger of sounding self-congratulatory.
When your ratings are plunging through the floor, you just sound desperate.
Best to let the polls speak for themselves - as David Cunliffe did when asked for his reaction to this week's surprise-filled Herald-DigiPoll survey.
He would not be human if he was not cock-a-hoop at Labour's seven-point surge in support.
Wisely, he did not let it show.
Predicting the polls would ''bounce around'' in the months ahead, Labour's new leader simply noted that if the poll result was replicated at next year's election, then his party would be able to form a Government. He left it at that.
He did not need to state the obvious that the poll is significant as a huge morale-booster for the centre-left in two respects: first, in intimating (though not proving) that Mr Cunliffe's becoming Labour's leader is already making a very marked difference to the party's fortunes; and, second, persuading wavering Labour supporters toying with switching to the Greens or New Zealand First that a vote for Labour in 2014 now has much more value.
Of more immediate use to Mr Cunliffe is that the Herald poll has provided him with an unexpected source of the one thing he prizes right now - momentum.
From when he put his name forward for the party-wide election of the new leader, Mr Cunliffe has sought to jolt domestic politics out of the National-controlled status quo by blitzkrieging his way into the public's consciousness. He is hellbent on getting the public to start listening to Labour again.
To that end, Mr Cunliffe has a schedule which should keep him almost constantly in the public eye this side of Christmas as he heralds a ''new beginning'' for Labour, a phrase which implicitly acknowledges the public got it right, while self-consumed, introspective Labour got it wrong.
The first step in transforming the party's tired, lacklustre image into a modern, dynamic and revitalised political brand came last Monday with Mr Cunliffe unveiling his shadow Cabinet.
There is an important upcoming speech to the Council of Trade Unions' conference early next month, which will be followed by Labour's own conference in early November, which will be followed by the Christchurch East by-election campaign.
This week's Herald poll is a bonus. Conducted after Mr Cunliffe became leader two weeks ago, the survey's findings beg the obvious question of whether there is a direct causal link between his taking over and the sudden lift in Labour's support and a corresponding drop of five points in voter backing for National.
However, if the dramatic closing of the gap between the two main parties from nearly 18 points in the previous Herald poll in June to just six points this month was solely down to Mr Cunliffe, then he surely would have enjoyed an even more spectacular performance in the preferred prime minister rating than the near 17% he scored.
The poll's respondents were clearly well aware of the change in the Labour leadership.
Only 1% of those backing Labour singled out David Shearer as preferred prime minister.
However, that did not automatically translate into wholesale endorsement of Mr Cunliffe. More than half of those who said they would give their party vote to Labour opted for someone else as preferred prime minister - John Key, Winston Peters, Helen Clark, Phil Goff, Russel Norman or Grant Robertson and in that order. In contrast, more than 95% of those giving their party vote to National favoured Mr Key as preferred prime minister.
A chunk of Mr Cunliffe's's rating came from Green voters who scored him nearly as highly as Dr Norman - recognition perhaps that the Labour leader will be the prime minister in any governing coalition forged by the two centre-left parties.
If Mr Cunliffe's impact was somewhat subdued, the narrowing of the gap between National and Labour is harder to fathom.
What might be happening is that the wear and tear on National's reputation from various earlier debilitating sideshows and botch-ups is finally showing in the polls.
Voters' attitudes as to how they will cast their vote are slow to change - more so with a government as pragmatic and unwilling to risk frightening the punters as the current one. There thus can be a long lag between cause and effect in the polls.
Mr Cunliffe may just be the beneficiary of that timing.
What is noteworthy is that in the preferred prime minister rating, Mr Cunliffe attracted support from equal quantities of male and female voters - unlike Mr Shearer, much of whose backing came from women voters.
This is important.
Labour has been doing well with women voters, but is missing out with men.
Fed up with the party's continuing penchant for the politically correct, the latter have switched off Labour and tuned in happily to Mr Key's moderate conservatism or found comfort in Mr Peters' economic nationalism and more hard-edged social conservatism.
But Labour has been here before.
Back in March, the Herald poll flattered to deceive with support for Labour jumping to more than 36%. Unfortunately for Mr Shearer, those gains evaporated.
That it might happen again is ample reason for Mr Cunliffe to continue to be cautious when it comes to talking up opinion polls.
- John Armstrong is The New Zealand Herald political correspondent.