Nominations have closed for the SNP's depute leader contest.

The party has received four eligible nominations to stand for the position.

On the ballot will be MPs Angus Robertson and Tommy Sheppard, MEP Alyn Smith and a councillor, Chris McEleny.

The position is available following the resignation of Stewart Hosie MP.

Hosie's extramarital affair with a political journalist was made public in a newspaper and he resigned a short time later citing health reasons. He said he was suffering "stress" caused by the "intense scrutiny" of the media.

Though the position may only have minor public interest, and its powers restricted to the internal matters of the party, it has been a gateway office or bigger things.

The last five leaders of the SNP - Nicola Sturgeon, Alex Salmond, John Swinney, Gordon Wilson and Billy Wolfe - have all served as depute leader at some stage in their careers.

Above all else, the office gives its holder a platform to shape and influence party policy.

Around 120,000 SNP members will have a vote in the contest which will be decided through a Single Transferable Vote System. Members will rank their candidates in order of preference.

The candidate with the least votes will drop out at the end of each round until one candidate gets over 50% of the vote and is declared the winner.

Here are the four candidates:

The Moray MP is considered the front-runner in the contest.

Robertson serves as the party's Westminster leader which means he is the SNP's spokesman at Prime Minister's Questions.

Part of the Moray MP's pitch is to create a balance in the party's leadership between urban Scotland, which Sturgeon represents, and rural Scotland which Robertson represents.

He joined the SNP as a teenager in the 1980s and eventually became an MP in 2001.

As well as Westminster leader of the party, Robertson has served as the party's business convener, which involves chairing the SNP's national executive committee and its policy making forum.

Robertson chaired the party's 2007 and 2011 Scottish Parliament campaigns and led the party's change of policy on Nato membership.

The change in policy was controversial in the party and it passed at the 2012 conference narrowly.

His association with the policy and the impression he is further to the right than a lot of members' politics may turn some to the other candidates.

Despite being a fresh face in the party, Sheppard's profile is high among its members.

He joined the SNP three days after the Yes campaign lost the 2014 independence referendum.

Just seven months later he was sworn in as the honourable member for Edinburgh East with a 9000-strong majority.

This is not Sheppard's first foray into politics, however. He was elected as a Labour councillor in 1986 in Hackney, London, and was made deputy leader of the authority in 1990.

At the 1992 general election, he stood unsuccessfully in the safe Conservative seat of Bury St Edmunds.

He returned to Scotland and went on to found and manage the Stand Comedy Club.

In 2003, he left the party because he could "no longer bring myself to vote Labour" as his "outlook has barely changed but clearly the Labour Party has".

Sheppard is proposing SNP branches become more discussion led and wants to see, as does Angus Robertson, paid campaigning organisers installed across the country.

As a relatively fresh face, the Edinburgh East MP may attract support from the around 94,000 party members who, like him, joined in the wake of the referendum.

Smith believes he is the right man at the right time for the SNP.

With the First Minister saying Brexit represents a change in circumstances which could lead her to proposing a second referendum on independence the MEP believes his European credentials could help the party.

He said: "My pitch for depute is a simple one. Now's the time. We must embrace Europe and put the European question at the heart of how we do business as a party, at home, as well as in the wider world.

"We need to make clear, to ourselves as a party, to Scotland and to the wider world, that we choose Europe as our future, Westminster is our past."

Smith was elected to the European Parliament in 2004 and re-elected again in 2009 and 2014.

Like Robertson and Sheppard, the MEP also wants to see paid organisers installed by the party.

He has also opened the door to a change of party policy on the monarchy.

Smith has said he is "up for" a referendum on its continuation after independence.

McEleny is the outsider in the contest among the four.

But, as we have already witnessed in the last 12 months, nothing is certain in politics.

He was elected to serve as a councillor for Inverclyde West in 2012 and went on to head the SNP's council group.

The councillor is the only candidate who is not a parliamentarian but he would not be the first nationalist to hold a senior internal role despite not being elected to a parliament.

Dr Allan Macartney was elected as depute convener in 1992, two years before he became an MEP.

Indeed, Billy Wolfe never held public office but was leader for a decade.

McEleny has planted his campaign firmly to the left of the party. He has declared himself a socialist and also a republican.

The outsider wants to balance the party with less emphasis on parliamentarians and more on councillors.

He points out that the party has far many more local councillors across the country than they do MSPs, MPs and MEPs.

McEleny's election would be viewed as ordinary party members elevating one of their own to the senior role.

The outsider's campaign has been endorsed by former depute leader and outspoken Nationalist figure Jim Sillars.