Just 246 votes separated Mr Hendy on Sunday from sitting MP Mike Kelly and electoral authorities have warned that it could be as late as September 20 before winner of the contest can be declared.

Both candidates in the ''bellwether'' electorate, which has gone with government in every election since 1972, were lying low on Sunday, declining to be interviewed or photographed.

There will be a recount of polling day ballots on Monday morning and counting of pre-poll and postal votes will not get under way until Tuesday.

The latest Australian Electoral Commission figures published on Sunday had Mr Hendy, a former chief executive of the Australian Chamber of Commerce and Industry, leading on 50.17 per cent to Dr Kelly's 49.83 on the two-candidate preferred count.

However, with several polling places yet to report and the pre-poll and postal count still to come, both sides believe the seat remains too close to call.

The booth-by-booth count shows that Dr Kelly, the former army officer who has held Eden-Monaro since 2007, easily outpolled his opponent in Queanbeyan, just across the NSW border from Canberra.

Dr Kelly polled as high as 61.34 per cent in the Queanbeyan South booth on a two-candidate preferred basis while Mr Hendy did not manage any more than 48.43 per cent in the vital town.

However, the sitting member had mixed fortunes in the sprawling electorate that extends to the Victorian border and Snowy Mountains.

Mr Hendy is dominating the count in several important regional centres, including Jindabyne in the mountains and Merimbula on the coast.

In the important fishing town of Eden in the south of the electorate, Mr Hendy is well ahead on 59.82 per cent to Dr Kelly's 40.18 on a two-candidate preferred basis.

In Canberra's seaside playground of Batemans Bay, Mr Hendy is in front in two of the town's three polling booths.