Bill Shorten has conceded Labor's star candidate Kristina Keneally remains the underdog just a week out from the Bennelong by-election, despite a high-profile campaign.
But the Labor leader said the former NSW premier could wrestle the Sydney seat away from Liberal candidate John Alexander.
"Kristina certainly is the underdog in terms of not being the favourite here ... but I think she is a dynamic candidate," Mr Shorten told reporters on Friday.
"We're going to take every opportunity over the next eight days to make sure that people realise they have an opportunity to send a message to Malcolm Turnbull."
Mr Alexander resigned in November amid speculation he held dual British citizenship, sparking the December 16 by-election.
Mr Shorten and Ms Keneally addressed the media outside Ryde Hospital on Friday, taking aim at the federal government's health record.
Mr Shorten said statistics from northern Sydney's hospitals and clinics were a "dismal roll-call of poor performance" that revealed thousands of people on long waiting lists for elective surgery.
Thousands more were unable to see doctors and specialists because of rising costs, he added.
Ms Keneally accused her rival of having a hand in the closure of an Eastwood Medicare office when it reportedly merged with Centrelink in 2015.
"You broke it, you own it, and you fix it. Well John Alexander hasn't fixed it - we'll fix it."
Ms Keneally challenged her rival to a debate on health care in Bennelong, likening it to the famous 1973 "battle of the sexes" tennis match.
But Mr Alexander, speaking at a separate press conference in Epping, suggested Labor was responsible for the closure because of a policy implemented back when the party was in power federally.
"Kristina closed the Eastwood Medicare centre and 128 other Medicare centres," he told reporters, adding his electorate has among the highest bulk-billing rates in Australia.
Mr Alexander said he would welcome a debate providing Ms Keneally was truthful when it came to statistics about medical services in the electorate.