You might have thought that the Lib Dems don't get too cross about anything - but the personal tax threshold has really got them going.
More specifically they feel that the Tories have stolen their policy on this and dressed it up as their own.
The personal tax threshold is the level at which we all start paying tax - it is due to go up to £10,500 in April.
So that means if you earn below that amount you pay no tax at all.
At the Tory Conference last week - the Prime Minister announced that the Conservatives would raise the level further, so that by 2020 it would reach £12,500.
"Thieves!" cried the Liberal Democrats, who say it was their idea first.
Today they will try and snatch the initiative back.
Nick Clegg is doing his big broadcast interviews this afternoon.
He will be announcing that not only will the Liberal Democrats take the personal tax allowance up to £12,500, they will start right away.
So in the first year of the next Parliament it will go up by £500.
That would put around an extra £100 in people's pockets.
It will cost too, of course, a rather eye-watering £1.5 billion.
The Tories were criticized for not having any detail on how they would afford it.
The Liberal Democrats are promising they will be announcing where the money is coming from.