While it was a night of celebration for the new MLA it was a bad one for the Gunner NT Government he joins with Labor's winning margin in the Darwin seat it has always held cut by 10 per cent from the last election to five per cent.

The size of the swing against Labor casts doubt over Michael Gunner's position as NT chief minister.

Some Labor insiders want him replaced before the general election in August, when Mr Bowden will have to compete for Johnston for a second time in less than six months.

The vote was sparked by the resignation of former minister Ken Vowles last year, who was removed from caucus after a public and bitter row with Gunner.

Labor and Mr Bowden arguably only won because the conservative vote was split due to the new Territory Alliance party led by former Country Liberal chief minister, Terry Mills which fielded a candidate for the first time.

The Territory Alliance candidate Steven Klose finished second and received more votes than the CLP's Josh Thomas and is now a legitimate contender.

Mr Thomas only finished in fourth place behind Greens candidate Aiya Goodrich Carttling in what was a poor performance by the Country Liberals.

If Mr Klose had won it would have threatened their opposition status and there is still the possibility of that independent MLAs such as Jeff Collins considering joining the new party.

Territory Alliance's strong showing will be a worry for the CLP ahead of the August election.

Australian Associated Press