MP Jim Murphy is the early ­frontrunner in the race to succeed Johann Lamont as ­Scottish Labour leader.

The Sunday Herald has spoken to MPs, MSPs and councillors who are ready to back the shadow international development secretary for the top job.

Party sources believe it is "likely" an MP will win, with former prime minister Gordon Brown and deputy leader Anas Sarwar also being mentioned in dispatches.

Left-wing MSP Neil Findlay is also being spoken of a potential candidate.

Although Murphy has always seen himself as a Westminster politician, the MP's allies believe he is keen on a Holyrood switch and is enthusiastic about becoming leader.

However, his path to Holyrood is complicated and he could probably only become an MSP in 2016.

It is unlikely Murphy would want to become a List MSP, or risk his prospects by trying to unseat a sitting SNP MSP, so he would require an incumbent Labour member to stand down.

Insiders say Murphy could stand for Renfrewshire South if sitting MSP Hugh Henry retires, or go for the Motherwell and Wishaw seat, if 67-year-old MSP John Pentland made way.

Murphy's Blairite politics could also be an obstacle.

As a minister in the Blair and Brown governments, Murphy supported the Iraq war, ID cards and tuition fees.

A source close to Murphy said: "It feels like Jim's time. He had a great referendum and would bring a real energy to the job."

Sarwar would face the same practical challenge of finding a seat if he became leader.

However, the 31-year-old MP is considered by some party insiders to be too young and inexperienced for the job.

His decision to send his son to a private school in Glasgow may also count against him.

Brown, who hinted at a Holyrood candidacy during the referendum campaign, is believed to be the least likely of the trio to stand.

Although he was politically re-energised in the pro-Union campaign, allies of the former prime minister think a return to leadership is unlikely.

Linlithgow and East Falkirk MP Michael Connarty has backed Brown for the job, saying he is "a towering figure" who was "speaking the language of the people of Scotland".

Findlay, a Lothians MSP elected in 2011, could become a standard-bearer for the Left in any leadership campaign and attract trade union support.

Sources say electing an MP as leader would make choosing an MSP deputy a necessity, with the post-holder having to take part in First Minister's Questions until 2016.

Two first-term MSPs - Kezia Dugdale and Jenny Marra - are the most likely to stand if Sarwar vacates the deputy post, with experienced MSP Jackie Baillie being another option.

A key element of the contest will be the electoral system. Following the Falkirk candidate selection debacle, Ed Miliband replaced Labour's historic electoral college with one-member-one-vote (OMOV).

However, Lamont did not implement OMOV for Scottish Labour leadership contests and, unless a special conference is called, the old system will be used.

This would mean one-third of votes going to affiliated trade unions and societies, one-third going to MPs, MSPs and MEPs, and the remaining 33.3% being handed to ordinary members.

The college system has attracted widespread criticism and has even been referred to as one-member-four votes: an MSP who is a member of two trades unions could get multiple votes.

Another issue is the lack of capacity in Labour's Glasgow headquarters to run a leadership contest.

With Lamont and also general secretary Ian Price going, insiders say it would be difficult to expect interim staff to organise a potentially tricky leadership contest.

Sarwar is to become interim leader and a party official is expected to take over as acting general secretary.

A meeting of the Scottish Labour executive committee will meet today to discuss the election.

John Park, the assistant general secretary at the Community trade union, said: "Given Ed Miliband changed the electoral college for UK leadership elections, it would be sensible for the Scottish party to follow the same process. The electoral college is outmoded and outdated."

Pat Rafferty, Scottish secretary of the Unite union, said: "Unite, as the biggest affiliate to the Labour Party, will be ensuring our members participate fully in this election and that their views are given full voice as we choose Labour's new Scottish leader."