JIM Murphy is filling "a gap in the market" for the No campaign, he says.

Since June 10, the start of the 100-days countdown to the referendum, the Labour MP for East Renfrewshire and former Scottish Secretary has been on the road with his "100 towns in 100 days" tour on behalf of Better Together.

Ever relaxed, he concedes it's partly hype. He's not actually on the stump for 100 days (he's just back from a camping break, for instance), nor is it 100 towns, but 100 street meetings, often several in one town.

But he's still putting in a hard shift, driving himself around the country, working busy halls and quiet street corners alike.

"There's more than enough people doing this sort of stuff in the Labour Party," he says.

"On the Better Together side there wasn't, so I thought, 'I'll do that'. I don't want to be stuck in the office for the next three months."

It's not because he and Scottish Labour deputy Anas Sarwar - seen as a future rival for the Scottish leadership - are having friction that he's out for Better Together, not Labour?

"No, definitely not," he splutters. "I'm a man without friction. Friction free! Friction free! No, definitely, definitely not."

When the Sunday Herald caught his act last week, Murphy was wooing two dozen folk in a Falkirk playpark, a venue even he called "weird".

He's more Alan Partridge than Tommy Sheridan, more conversational than firebrand. But after 45 minutes of chat and question-and-answer he'd thoroughly charmed his small audience.

He also effortlessly handled a passing Yes heckler by inviting him over to make his point. The man stalked off with an impotent grumble.

"Place is hoachin' with them," tutted a Labour voter in the crowd, illustrating Murphy's true task - to shore up support in Labour areas where the Yes message that independence would end Tory rule in Scotland is winning converts.

Murphy's messages are few and simple. The Conservatives, for all their ills, can be voted out, but independence is forever.

"You don't have to change your passport to change your government," is a favourite line.

He also says the SNP haven't proved the case for independence and are hiding the downsides; asking questions is not negative, but healthy; the bigger the change, the bigger the risk; the UK has genuine international clout; and the Union, like a trade union, protects its members. His bottom line: Why take the risk?

Away from the tour, Murphy has of late taken over Lord Foulkes's mantle as "cybernat-finder general", policing what he calls the intolerance on the Nationalist fringe.

He says he's particularly unhappy about people on the Yes side filming No canvassers on their phones. It happened in Falkirk last week, he says, and has also happened a few times in Glasgow, he says.

"What the f***'s going on? I don't know how it's organised... but somehow, somewhere, there's been a wee kind of push given to the harder end of Nationalism to video anybody on the other side.

"It's weird, it's unhealthy, and it's aimed at intimidating."

It doesn't bode well for September 19, he says.

"Whatever the outcome, we're going to have to live together as friends and neighbours again.

"It does worry me when you've got people wandering around filming folk."

But is it worse than Murphy repeatedly telling SNP MP Pete Wishart to "f*** off" in the House of Commons, as was reported in February? He grins and doesn't deny the incident.

"Pete and I don't always see eye to eye and had cross words. We shared industrial language with one another. There was one SNP MP who came up to me after it and said: 'I've been wanting to talk to him like that for years.'"

One of the most prominent Catholics in Scottish politics, Murphy says he welcomes the recent entry of Faith in the Union, the No vehicle set up by Labour peer Willie Haughey, to the debate, as well as Christians for Independence."People of faith have a voice," he says.

Although he says he's not worried about a sectarian strain arriving, mention of the Orange Order registering as an official campaign group turns his mood unusually grim.

''I'm 46, and I've never had anything to do with the Orange Order and I'm never going to have.

"Not for a moment would they be part of the Better Together campaign. They'd be unwelcome.

"These other faith organisations … appear to be all-welcoming. The Orange Order exist for a different purpose.

"Their unsavoury history ... no matter how you slice and dice it ... it's not an inclusive organisation. They've got a vote so they should have a voice, right? But we'll find no common cause with them."

Amid speculation that Johann Lamont has resigned herself to not being First Minister and may quit as Labour leader before 2016, Murphy is now being touted as the Scottish party's saviour.

Does he fancy a flit to Holyrood? "I'm pretty settled. I'm happy where I am. No, it's not my thing. I'm looking forward to serving in Ed Miliband's next Cabinet."

It sounds firm, but he's not ruling himself out.You come away with the impression that when a gap in the leadership market arises, he'll probably want to fill that one too.