* Turnout to be crucial at June 23 referendum

* "In" campaign targets young as pro-EU demographic

* Apathy of youth contrasts with motivated eurosceptics

By William James

MANCHESTER, England, May 18 (Reuters) - Saim Chowdhury is the kind of Briton keeping pro-Europeans awake at night with five weeks to go before a referendum on EU membership: young, educated and supportive of the economic arguments for staying in, he doesn't plan to vote.

With public opinion divided down the middle on the issue, Chowdhury is one of millions that 'In' campaigners fear may not bother to vote, which could tip the balance towards Britain leaving the European Union.

It's not as if the stakes aren't high. Leaving the EU would throw Britain's trade, security and global leadership role into question; staying in could shackle it to a bloc struggling to manage crises on many levels, including mass migration.

But for Chowdhury and his friends, business management students chatting about deadlines outside Manchester Metropolitan University, those concerns don't quite penetrate the bubble of student life.

"You know it's not like we don't care, it's just that we're not thinking about it right now. If it's not affecting us now, why would we do anything about it" said Chowdhury.

The apathy extends far beyond the student community, meaning that getting people into the polling booth is one of the biggest challenges for the "In" campaign, especially given the enthusiasm of their eurosceptic rivals who want to get out.

"There are plenty of 'quiet remainers' who on balance think we should stay in the European Union, but they have no great passion for the European Union," said James McGrory, spokesman for the "Stronger In" campaign. "There are people on the other side of the argument who have spent their lives wanting this -- it's a massive, massive deal for them."

As a result, the campaign is piling its resources into increasing turnout on June 23, especially among the young.

Polls show younger voters are more pro-European than older generations: 56 percent of 18- to 34-year olds would vote to remain in the EU, compared with 33 percent of those aged over 55, according to polling firm Opinium.

"They are a group of people for whom less persuasion is needed because they're pretty much on our side of the argument," McGrory said.

GOING AGAINST THE TREND

Unfortunately for the 'Ins', young Britons tend not to vote.

An estimated 43 percent of 18- to 24-year-olds took part in last year's national election, far below the overall turnout of 66 percent and consistent with previous elections, where turnout in that age bracket has been below average since at least 1964.

One of the campaign's prime targets is university campuses, which offer a high concentration of people who fit the profile of a likely EU supporter: the right age, well-educated, with an international outlook and eyeing their future careers.

To reach the country's 1.8 million university population, the 'In' campaign last month held a "Brighter Futures In" bus tour of campuses, meeting with student activists and training them how to spread the message to their peers.

Asked how they thought staying in the EU would affect them, Chowdhury and his friends reinforce the idea that students instinctively reach conclusions that match those promoted by 'In' campaigners.

Thinking out loud, they reason that leaving would limit opportunities for their generation to work overseas and deprive British businesses of skilled foreign labour.

"People fail to realise that with people coming in from the EU ... there's also skills that are coming in to this economy," Chowdhury said. "Whereas if you've got really strict rules, there could a lot of downfall in output and stuff like that."

Turning those ideas into action on June 23 will be no mean feat. Data shows 18- to 24-year olds are the least likely to vote in the referendum because they either don't see what it has to do with them or are disinterested because they feel the political system doesn't represent them -- fueled in large part by government decisions to raise university tuition costs.

The key to raising student turnout is making the referendum relevant, said Ally Routledge, a politics and history student who volunteered to take part in the "Brighter Futures In" tour.

Routledge, 20, joined 14 other students at a workshop with one of Manchester's members of parliament to brainstorm how to counter anti-EU arguments on issues like immigration and use debates and other campus activities to drive home the idea that the outcome will have serious implications.

"I'd say 'It really matters for your future'. You're going to be graduating in a few years, and you don't know what job you're going to have. Look how many people are willing to pull their companies from the UK," she said.

UNPOPULAR LEADERS

It doesn't help that the 'In' campaign is led by Prime Minister David Cameron, head of the ruling centre-right Conservative Party which is unpopular with many young people.

A poll conducted after the 2015 election showed that 59 percent of students voted for either Labour, the Liberal Democrats or the Green Party -- all of whom sit to the left of the Conservatives. The leftist Labour Party alone garnered 39 percent of the vote, 20 percentage points more that the Conservatives.

This means the role of Labour is key. But although the party officially backs Britain staying in the EU, strategists fear leader Jeremy Corbyn is not fighting hard enough.

Corbyn, who voted 'No' to Europe in a 1975 referendum, became party leader last year largely on the phenomenal success of his socialist agenda with the young.

"Cameron does not necessarily appeal to everyone. Corbyn is critical in this," one campaign source said, speaking on condition of anonymity.

The 'In' campaign is also working to overcome practical difficulties. Students often have no fixed address and, because they don't tend to vote in general elections, are frequently not on parties' databases.

"One of the things they've been doing aggressively in the universities is encouraging people to register to vote, telling them how to do it, telling them when the (June 7) deadline is," said McGrory.

University examinations started in early May and go all the way to the end of June, with students returning home throughout the period. This means they will likely be at a different address for a reminder visit when the referendum rolls around.

"The traditional knocking on doors exercise is a complete waste of time," Manchester-based Labour MP Lucy Powell said.

The referendum also falls in the middle of the Glastonbury music festival, attended by around 135,000 people, and during the hugely popular soccer European Championships in France.

With so many issues competing for students' attention, Benita Birak, a second-year digital media and marketing student, summed up the challenge for the "In" campaign.

Sitting 20 metres away from the campaign bus, she admitted she didn't really understand what the referendum was about.

"If I do some more research into it, then yeah more than likely I'll vote," she said. "But if I don't get time to research then it'll probably be a situation where I don't."

(Editing by Sonya Hepinstall) ((william.james@thomsonreuters.com; +44 207 542 3374; Reuters Messaging: william.james.thomsonreuters.com@reuters.net))

Keywords: BRITAIN EU/TURNOUT