And for Nationals' candidate and current member for Monaro, John Barilaro, and his Labor candidate Steve Whan, it's as high-stakes as it gets, with both men saying they'll retire from politics altogether should they lose the contest.

Mr Barilaro and his family voted at Jerrabomberra Public School this morning at 10am. He said it'd be a tight race between the two candidates, but backed the bellwether seat traditionally going with Government to help get him over the line.

"It is a tight race, it's the bellwether seat and a marginal seat. It's not by accident it's gone 25 out of the last 28 elections with government," Mr Barilaro said. "I'm looking forward to history repeating itself and that remaining.

"I'm confident, but it will be a tight race. I'm not even sure we'll actually get a result this evening," he said.

Meanwhile Mr Whan voted with his family at their local booth of Karabar. He said he's now attended so many elections at his local booth at Karabar High School that it was hard for him to tell whether the greetings from voters were a political endorsement, or just friendly neighbourliness.

"It's very hard to tell. There's a lot election campaigns I've done here [at Karabar] now. I usually get a positive response from people personally, but you don't really know how they're voting when they go in. So I'm not taking anything for granted," he said.

However he also predicted a close race in the bellwether seat, and said many voters were still undecided.

"I was certainly talking to people in the last two days who told me they'd make up their mind when they got to the polling booth," Mr Whan said. "So it's very important that I'm still talking to people, that we're still out there with our message right up until 6pm."

Around eight to ten thousand Monaro voters have voted by pre-poll this election- around a third of the electorate. Mr Whan said when the pre-poll results came in it'd be a fair indication of which way the bellwether would swing.

"We should have some big booths in by 8pm or so. And there's around 8,000 pre-poll votes which the electoral commission will start counting at 6pm. So that's now the biggest booth, so that's quite critical.

"I would have thought that when we get pre-polling in and Jerrabomberra, Karabar and a Cooma booth, we'll have a reasonably good idea of how we're going," he said.

John Barilaro was experiencing similar support from locals over at Jerrabomberra, and said he'd been enriched by his term as Member for Monaro so far.

"I've had many good wishes in relation to today's election," he said. 

"Today, people will cast their vote. I'll accept the verdict of all the voters of this electorate. It's been an absolute honour and a privilege to serve them. I've learnt so much and have been enriched by the experience.

"On a policy front, this government's been a good government. We've accomplished a lot, we've turned the state around and the vision we've got going forward is significant."

Meanwhile, the odds have widened on Sportsbet in favour of the Labor candidate, with Steve Whan now placed at $1.30 to John Barilaro's $3.30. 

Polls close at 6pm.