Poll: This surprising group of undecided voters holds the key to the Brexit vote
The ComRes poll for the Sun newspaper found that 21% of female voters are undecided and 14% of male voters are undecided.
More specifically, female voters, unskilled voters, people aged 45-54 and people living in the North of England were the most undecided group of voters.
This means there's a surprising group of middle-aged female manual workers living in the North that the Leave and Remain campaigns need to reach.
There are 17 million undecided voters, while 23% of undecided voters are 45-54 year olds, only 13% are aged 22-34 or 55-64. And, while 24% of manual workers/benefit claimants are undecided, only 14% of high paid professionals in managerial positions are undecided.
Data like this will be vital for the official EU referendum campaigns Britain Stronger in Europe and Vote Leave. They are both strictly limited to spending £7 million - around £4 billion was spent on the last US presidential campaign. It is vital for both groups that they target their resources at the demographics that need reaching.
The ComRes poll also showed that the Remain campaign faces an additional problem - only 49% of people who say they will vote to remain in the EU actually like it.
Polls keep showing that Remain voters are much less motivated to go out and vote, so the Remain campaign both has the job of convincing undecided voters that remaining in the EU is a good thing and convincing their own supporters that it's worth voting.