``Absolutely, I'm feeling the pressure,'' he admits.

Who wouldn't, taking the place of Greens leader Bob Brown in the Senate in a crucial contest for the party's future.

Under new leader Christine Milne the Greens are desperate to hold the balance of power in the next Senate, and wield the power that comes with it.

That all depends on this Senate election, where he replaces Dr Brown after a ``stellar'' vote of 20.3 per cent in 2010 built around climate change.

``This year it's asylum seekers and tertiary education that we're hearing as the two biggest issues,'' Senator Whish-Wilson said.

The Greens say their polling shows the party right on the quota needed to elect Senator Whish-Wilson, who maintains ``confidence without taking anything for granted''.

Senator Whish-Wilson is right to be cautious: despite their low profile, Senate elections are unpredictable and unforgiving.

For Labor and the Liberals, it's all about your position on the party list.

Strong public support for the major parties means the top two positions are guaranteed to be elected - in 2013, that's Labor's Carol Brown and Catryna Bilyk and the Liberals' Richard Colbeck and David Bushby.

Internal brawls dictate the ticket order, particularly as it guarantees you six years in Canberra.

As parties must reach 43 per cent to guarantee a third seat, only hit once by the major parties since 1998, Labor's Lin Thorp and Liberal Sally Chandler are walking the tight-rope.

Throw Senator Whish-Wilson - seeking to pass the magical ??14.3 per cent mark of a quota - into the mix and you've got a three-way battle for two seats.

Each of the three could miss out, changing the Senate's delicate balance.

Labor Senator Lin Thorp, who entered Parliament alongside Senator Whish-Wilson after Labor stalwart Nick Sherry resigned, has known defeat.

In 2011 she was defeated in her Legislative Council election, but is going into this election ``confident and determined''.

``Obviously the third seat is a difficult seat to win for any party, but it's vital Labor wins to maintain our big voice for our small state,'' Senator Thorp said.

Senator Thorp will campaign alongside Labor's House of Representatives candidates over the next month, hoping a stronger vote translates to the Senate.

Labor sources claim internal polling showing a ``line-ball'' contest for the sixth seat between Senator Thorp and Liberal newcomer Sally Chandler.

Ms Chandler, an international trade specialist who resigned her federal government role at the weekend, said angst at the economy would disadvantage her opponents.

??``The Green hand on the shoulder of government in Tasmania, and nationally, has caused a tremendous amount of pain,'' Ms Chandler said.

``People are telling me I've got a very good chance but I know I have to work hard every step of the way ... there is a long way to go.''