Careless words cost votes and deputy Labour leader Harriet Harman has just had that lesson dramatically reinforced after a radio interview which allowed the Tories to quote her saying middle income earners should pay more tax.
David Cameron threw it at Ed Miliband twice during their final question time clash of the summer, partly to avoid answering a question about when he was planning to publish his tax returns as promised, but also to give Tory troops some ammunition to fire through the long break.
The words in question were not at issue, and they clearly did catch out Miliband and shadow chancellor Ed Balls, whose expression of disbelief and puzzlement was a picture.
Harman had indeed said: "I think people on middle incomes should contribute more through their taxes."
It even led to an instant Tory tweet with party chairman Grant Shapps stating: "Harriet Harman has let the cat out of the bag: Labour want to raise your taxes."
A great coup for Cameron and his bid to paint Labour as ready to attack the so-called "squeezed middle" they claim to care for.
Except for the small fact that - yes, you guessed it - it isn't true. Harman has now fired off a letter to Cameron accusing him of "lying" and sending him her full quote.
The words were part of a much longer answer about the UK's system of progressive taxation which means the more you earn the more you pay, a system all parties have long supported.
It begs the question of whether Cameron still supports the progressive principle. Of course he does.
But it is also a lesson for Labour as it approaches the election and, to be fair, it is a lesson it should have learned years ago, politicians have to watch every single word for the way it might be taken out of context and thrown back at them.
On this one, Harman was just loose enough to allow her words to be misrepresented.
It's going to be a rough campaign.
Male, pale and stale hacks
Transport secretary Patrick McLoughlin addressed a lunch with political journalists in Westminster secure in the knowledge he had not fallen victim to the prime minister's cull of the "male, pale and stale" ministers.
He noted, with a little barb, that he was addressing an audience of predominantly white, grey-haired men.
Picture of the week
European leaders were on the edge of their seats to witness the moment David Cameron met Jean-Claude Juncker in Brussels, for the first time, after spending weeks trashing him in the international media. It didn't disappoint.
The two mean appeared to engage in a rather clumsy and not quite successful high-five greeting. (It recalled the toe-curling "Yo, Blair" greeting the former PM got from George Bush at one international meeting.)
One wag suggested what actually happened was Juncker went to slap Cameron around the head but the prime minister countered it with a quick slap-back of his own, so resulting in a high five collision.
When a majority isn't enough
Union leaders are facing a new Tory law that no strike vote would be deemed legal unless more than half of all of a union's members had cast their vote in a ballot. Really?
How exactly would future ministers defend this move? Would they declare that such a majority turnout would be needed for union leaders to have a mandate, or to allow any union to take action that could affect ordinary members of the public.
Take out the word "union" and replace it with "political party" and the absurdity, not to mention injustice or hypocrisy of such a law would appear obvious, wouldn't it?
Apparently not to political leaders who seem to believe they really do operate by different rules.
As Unite's Len McCluskey pointed out: "not a single member of the present cabinet would have been elected using the same criteria."
Quote of the week
William Hague has always been cherished for his wit and there will be new occasions to enjoy it now he is leader of the Commons.
And he deployed it to devastating effect during his very first outing in his new job when asked if he could stage an emergency debate on the bedroom tax because of the Liberal Democrats' demands for changes to it.
He rejected the request, saying: "I don't think we will be able to have an emergency debate every time they change their policy".
The coalition is still going well, then.