Trump demands prosecution of Alaskan Democrat over spoiler candidate

US federal authorities have escalated a criminal investigation into the Alaskan Senate race following allegations that Democratic candidate Mary Peltola's campaign coordinated to plant a same-name spoiler candidate on the ballot to siphon votes from the Republican incumbent.

Peltola denies knowing any other candidate on the ballot while US President Donald Trump calls the move "totally illegal."

The US Justice Department intensified its investigation into the Alaskan Senate race after a New York Times report detailing interviews, text messages and documents from Democratic candidate Mary Peltola's team aimed to coax a candidate with a similar name to the incumbent Republican senator into the race with the aim of confusing voters.

Daniel J. Sullivan Jr., a retired schoolteacher, has been included in the Alaskan Senate race ballot alongside incumbent US Republican Senator Dan S. Sullivan and Peltola.

Alaska's Republican Governor Mike Dunleavy ordered a separate state investigation, stating the deliberate manipulation of ballots directly struck at the "integrity" of elections.

The situation drew condemnation from the White House.

Speaking to reporters while campaigning in South Carolina, US President Donald Trump accused Democrats of "conspiracy."

"So they got a guy named Dan Sullivan to go up against on a ballot, Dan Sullivan.

So you split, it's called splitting the vote, totally wrong, totally illegal.

This is voter fraud at the highest level.

Not even that, he even looks a little bit like him.

Do you ever see the pictures?

It's the craziest thing I've ever seen." said Trump.

Meanwhile, addressing supporters at a rally in Juneau, Alaska, Peltola denied any wrongdoing or prior knowledge.

"I just want to clear the air.

I knew nothing about any other candidates on the ballot except for me and the incumbent.

That is all I have ever known about.

I am not interested in tricking voters.

I know I can beat Dan Sullivan." said Peltola.

On the streets of Juneau, residents remained divided over the controversy.

While some residents viewed the candidate manoeuvring as standard political strategy, rather than a criminal offence, independent voters expressed deep concerns the scandal provided fuel for critics to attack the democratic process.

"But it's not illegal and it is not unusual and so to me I'm really pissed off that the New York Times ran this article that puffed up something that is completely normal and not illegal." said a resident.

"I think there's no denying it and if I heard her say that it didn't happen or I don't know nothing about it, I would just at that point think even less of her because I'd believe she'd be lying." said an independent voter.

The controversy came as the country prepared for the upcoming mid-term elections with Trump's Republicans facing a strengthening Democrat opposition.