Mayo by-election tipped to be close

An independent candidate in the federal by-election for the seat of Mayo believes the result might not be known for some days.

The Adelaide Hills-based seat has always been held by retiring Liberal Alexander Downer.

But eight of the 11 candidates in Mayo are now directing preferences away from the Liberals.

Independent candidate Di Bell says that could make it tougher for the Liberals to claim victory.

"I think there's a shift in the electorate in terms of being prepared to entertain having an independent rather than party politics as usual," she said.

However Liberal candidate Jamie Briggs is still expected to win the ballot comfortably and believes Labor governments need to be sent a message about delivering water to the lower lakes.

"The only way to send a message is through a strong result for the Liberal Party," he said.

"What Mr Rudd, Mr Rann and the Labor Party want is an independent or a minor party elected."

Mr Briggs believes membership of a major party will give him the advantage over a large field of independents.

"They have a role in the Senate as a balance of power but in the House of Representatives they don't have an ability to pursue issues like the major parties do," he said.

The biggest challenge to Mr Briggs is expected to come from Greens candidate Lynton Vonow who stood for Mayo at last year's federal election.

The Greens are still confident they have a strong chance of beating Mr Briggs in the by-election.

Mr Vonow won 11 per cent of the primary vote in Mayo at last year's federal election.

He is confident of going a lot further today.

"It will be difficult but nothing's impossible," he said.

The Australian Labor Party is not contesting the by-election.