Cathy McGowan has warned the battle for the rural Victorian seat of Indi will be close, despite polling showing the independent MP holds a 10-point lead over her Liberal party rival, Sophie Mirabella.

The polling, commissioned by the Australia Institute, found McGowan had 37.3% of first preference votes to Mirabella’s 26.9%. But the Nationals candidate, Marty Corboy, had a support base of 10.6%, and the majority of those preferences would flow to Mirabella, McGowan said.

“I think it’s going to be competitive and close,” she told Guardian Australia.

McGowan holds the rural seat with a wafer-thin margin of 0.3%, after a mammoth effort in the 2013 federal election saw her snatch the seat from party stalwart, Mirabella.

Mirabella, a former shadow minister and confidante of former prime minister Tony Abbott, had held Indi from 2007.

McGowan said changing the electorate from a safe Liberal seat to a marginal independent seat had given voters more of a voice.

“It’s interesting that the community is responding to me as an independent and responding to the work we’ve been doing,” she said.

The polling found support for Mirabella was at its highest in the 65 and over age group, where two out of five voters would vote for her. By contrast, only 16.4% of 18-24 year olds would vote for Mirabella.

McGowan’s support is more evenly distributed across age groups, but 51-64 year olds responded to her best, with nearly half of voters in this age group saying they would vote for her.

The poll of 656 people was conducted by ReachTel on March 10.

Apart from political leanings, it asked whether voters supported greater funding for the ABC if it meant more remote and regional news services. Less than one quarter – or 22% – of voters opposed greater funding for the public broadcaster, with nearly 64% supporting it.

Mirabella supporters were more likely to oppose increased funding for the ABC, with just over 47% thinking more money was needed.

McGowan said she was prepared to fight an election campaign with a grassroots campaign that involved door-knocking voters and speaking at local events, similar to the campaign she ran in 2013.

She said she had been “getting out there” and speaking to voters face-to-face since taking office three years ago.

In August, then prime minister Tony Abbott backed Mirabella for Indi, saying she had learnt her lesson from her “shocking” defeat.

“It was a terrible disappointment to me and as well as obviously a disappointment to the Coalition and a great personal shock to Sophie,” Abbott told ABC radio. “This time rather than fighting and campaigning right around the country she’ll obviously be campaigning very locally.”

“She is a changed and better and more focused person as a result of the experience of the last election,” he said.

Despite suffering a 9% swing away from the Liberals in the 2013 election, Mirabella won preselection for Indi in June 2015.