Simon Sheikh and his fellow GetUp! activists are masters at grabbing headlines, raising cash and combating the conservative cacophony that dominates our airwaves and opinion pages.

But ask Canberra insiders about the group’s ability to influence policy and you’ll hear one word crop up again and again: overstated.

Former finance minister Lindsay Tanner tells The Power Index: “GetUp’s power is in setting issue agendas, not convincing governments to adopt specific policies.

“GetUp! has some influence, but politicians are conscious of the fact that it reflects a tertiary-educated demographic that is critical in the battle between Labor and the Greens, but not necessarily the battle to form government.”

Victorian Labor MP Steve Gibbons says: “I’ve long held the view that these bloody lobby groups, even if I’m sympathetic to their causes, are a f-cking nuisance. Because what it does is it just crams our inbox with crap.”

Some right-wing Labor MPs, we’re told, have taken to calling the campaigners “those f-cking GetUp! pricks”. Insults like armchair activists, remorseless self-promoters and political neophytes also get thrown around — even from comrades on the left. Liberal Senator Ian MacDonald caused a stir last month by referring to the group as the “Hitler Youth wing of the Greens political movement”.

The activist outfit, while talented at fundraising, also lacks the financial muscle to go toe-to-toe with cashed-up vested interest groups like the mining industry and the clubs.

Nevertheless, GetUp! is still one of the most influential lobby groups going around.

Look no further than the group’s long-running campaign on mental health. As well as collecting 100,000 signatures, GetUp! funded a TV advertising campaign, organised candlelit vigils in 50 towns and commissioned polling showing strong support for more mental health dollars. In this year’s budget, the Gillard government announced a $2.2 billion mental health package.

“The effect on government was tremendous,” says mental health advocate Ian Hickie. “We would have struggled to get the result we did without them.”

Mental Health Minister Mark Butler has publicly acknowledged the role GetUp! played in putting mental health on the agenda and forcing politicians to take action.

There have been other big wins, too. Even GetUp’s harshest critics admit the group sparked interest in David Hicks’ incarceration at Guantanamo Bay and helped turn public opinion around. GetUp! also played a crucial role in whipping up opposition to Labor’s plans to introduce compulsory internet filtering — a policy now opposed by both the Greens and the Coalition.

“These big national debates have a real impact on policy-making in Canberra,” Lachlan Harris, Kevin Rudd’s former press secretary, told The Monthly last year. “What GetUp! does is aggregate and amplify progressive voices and make sure they’re heard.”

Over a million Australians have signed one of the group’s petitions since 2005, according to GetUp!

Sheikh, GetUp’s national director, tells The Power Index: “In a handful of circumstances, we’re able to influence the exact policy settings, but primarily that’s not our job. Primarily, our job is to get issues on the national agenda and make sure our politicians are feeling the heat on them … We’re helping close the gap between information and action.”

Sheikh is adamant that GetUp’s influence stems from its 587,000 members, not his leadership. He insisted three volunteers participate in his hour-long interview with The Power Index at GetUp’s Sydney HQ. It’s an example of the earnestness that — like the exclamation point in the group’s name — aggravates some and appeals to others.

But there’s no doubt that Sheikh holds sway within the organisation. The son of an Indian-born industrial chemist, he’s mature beyond his 25 years — and always has been. His parents never lived together, so when his mother suffered chronic mental illness he became her primary carer. He was 10 years old.

*Read the full profile at The Power Index