Young people between the ages of 18 and 35 make up about 31% of the eligible voting population in the US, and they will soon be the largest group in the electorate.

Although they frequently talk about politics online, these so-called 'millennials' are traditionally less likely to vote than older people.

Developers have created a host of new apps targeting this age group.

But are they enough to encourage the smartphone generation to become more politically engaged?
'Tinder for politics'

Apps like Voter build on existing formats to introduce users to political candidates who align with their own beliefs.

Created by 26-year-old web developer Hunter Scarborough, Voter allows users to swipe left and right through a number of political candidates until they find the ideal match.

You could describe it as a political form of Tinder.

Scarborough says he created the app after becoming frustrated by the lack of political news sources he felt he could trust.

"I didn't want to vote on a sound bite from a news anchor, or a sound bite from a family member," he says.

"I looked at the wealth of raw political data becoming available, and realized there could be a much faster and more accurate way to become informed."

Scarborough is convinced apps like his can have a positive impact on turnout.

"If someone has a horse in the race, they're much more likely to participate," he says.

"So if you use the app and you have a strong degree of confidence in who you match for, you are much more likely to be at the polls when election day comes, " he adds.

Unlike Voter, the Brigade app - which builds on a Facebook-style model to encourage public political discussion online - does not allow users to choose whether to share their political information with others.

The social networking app works by asking a series of questions about political issues, allowing users to mark 'agree', 'disagree' or 'unsure'.

They can then see how they compare to their friends, followers and the wider population of users.

Brigade stresses the "huge potential" of apps to help younger voters get involved in politics, but recognises the difficulty in ensuring they remain interested.

"The hard part is getting to a scale that ensures people's voices and votes have real influence," says its spokesman Andrew Noyes.

"Those of us operating at the intersection of tech and politics must lead with issues millennials care about and find ways to keep them engaged by taking action with friends and neighbours."

'Need encouragement'

Other apps target specific social groups who are less likely to vote - such as Hispanic millennials.

According to the Pew Research Centre, roughly 11.9 million will be eligible to vote in 2016.

People in this age bracket make up a larger share of Hispanic eligible voters than they do among white eligible voters - 44% versus 27%.

The Unidos app aims to mobilise young Latino voters.

It was launched by Feet in 2 Worlds (Fi2W), a media project at The New School, New York City.

It provides users with a newsfeed with links to relevant articles, voting guides, emojis and links to other social media platforms.

"People who are less politically engaged need encouragement to register and vote," says John Rudolph, Executive Producer of Fi2W.

"We all understand that by working together and using a variety of approaches we have a better chance of breaking the historic trend of Latino under-voting."

But experts say although apps have the potential to encourage an interest in politics, they can only go so far in motivating 18-35 year olds.

One expert warns that political apps mainly appeal to young people "already highly engaged", looking for ways to connect with others online.

"They leave behind young people who are just not interested in politics, let alone doing something concrete in relation to the candidates and/or campaigns," explained Dr Kei Kawashima-Ginsberg, director of the Centre for Information and Research on Civic Learning and Engagement at Tisch College.

She points to the the "stalemate" in US Congress as a demotivating factor for young people and also to a lack of confidence amongst this group in political figures in general.

But she is keen to stress that millennials' lack of engagement in traditional politics should not be interpreted as an unwillingness to participate.

Hunter Scarborough agrees. "Millennials actually have the highest volunteering and community service rates than any other generation that came before them," he says.

"What that says to me is that there's a strong desire to have impact, but they haven't really seen the value in doing so through traditional methods."

Hunter Scarborough spoke to Deirdre Finnerty on World Update on the BBC World Service - listen to the interview here
'Real relationships'

But apps alone won't make the difference.

For Dr Kawashima-Ginsberg, a number of strategies are needed to increase engagement, boost registration and turnout.

She says there is still no real replacement for face-to-face contact.

"Candidates need to engage with them in person, and listen to what they have to say, instead of relying on the convenience of the apps to let young people find out about them," she says.