The seat has been held by former Liberal treasurer and retiring politician, Mike Nahan, since 2008.
One betting agency had Dr Krishnan as a $1.05 favourite to win the seat on March 13, with his Liberal opponent, Anthony Spagnolo, priced at $8.00.
As early voting commenced this week, Mr Spagnolo took a public swipe at Dr Krishnan for living outside the electorate, and preferencing anti-vaxxers.
He said a pamphlet promoting Dr Krishnan as a local who knew what it was like to live in the electorate was misleading.
“It’s concerning and goes to the credibility of their candidate,” he said.
Mr Spagnolo also questioned why the GP had preferenced anti-vaxxers ahead of the Liberal and Christian parties.
“During a pandemic, I think it sends the wrong message to the community,” he said.
Dr Krishnan – who recently received approval to administer the COVID-19 vaccine – said the decision to preference the anti-vaxxers party ahead of other party candidates was a decision made by the Labor party, and not him personally.
“As far as I’m concerned after one and two it really does not matter where the preferences go,” he said.
“I am working hard, that’s the only thing I can control.”
The Liberal party currently holds the seat of Riverton with a 4.2 per cent swing.