Simpson credits voters' switch as he romps home
The DUP's David Simpson remained cautious as the ballot count began for Upper Bann in the Eikon Exhibition centre at Sprucefield.
But there was little to worry about, and in the end he even credited supporters of other parties for increasing his winning lead by 10% to 22,317 votes.
He added almost 7,000 votes to his 2015 tally of 15,430, while the Ulster Unionist Party saw their share plummet well below the 10,000 mark.
UUP candidate Doug Beattie took only 7,900 votes, well down from Jo-Anne Dobson's 2015 total of 13,166.
"When we look at the vote it's plain to see that supporters of other parties have come across and voted for us and that will not be taken for granted," Mr Simpson said.
"We will prove that it was not a wasted vote for them and we'll continue to be thankful."
Speaking at midnight, Mr Simpson said he was already quietly confident about the result.
"If you analyse the Sinn Fein performance from the March Assembly election there were around 14,500 votes. We had 16,800 with two colleagues and I don't see an awfully big difference in that."
Finishing second with 14,325 votes - an increase of 3.4% - Sinn Fein's John O'Dowd said his party had still commanded a strong mandate for Upper Bann in the coming weeks.
"There are times for long and meaningful speeches, but at 3.40am this is not one of them," he told supporters after the official results announcement.
"We have a massive mandate for change, there will be a lot of hard and difficult talking over the next fortnight to try and restore our institutions and we will leave the meaningful dialogue for there."
Voter turnout for Upper Bann was recorded as 64.15%, with 51,431 ballots cast out of 80,168 eligible voters.
With all Ulster Unionist and SDLP MPs losing their seats, the UUP Assembly member Doug Beattie - a former soldier and Military Cross recipient - stressed the importance of being magnanimous both in victory and defeat.
Mr Beattie's share of the vote took a heavy blow of 12.5%, reflecting the second disappointing night at the polls for his party this year.
Earlier in the evening, he issued a warning to the Conservative Party about relying on the DUP.
"I would say, if they rely on the DUP they are relying on a party that won't allow same-sex marriage," he said.
Congratulating Mr Simpson on his victory later, he added: "It's absolutely right over the next five years that we hold him to account, but it's also right that the people of Upper Bann support him in his endeavours to represent this constituency."
The SDLP candidate Declan McAlinden finished with 4,397 votes.
Earlier in the evening, David Simpson praised Mr McAlinden's performance but predicted that if the SDLP's Dolores Kelly - who won her Assembly seat back in the March elections - had stood for Westminster even more nationalists would have gone to Sinn Fein.
Tara Doyle from the Alliance Party finished the night with 2,319 votes.