Labor has taken a battering over the past week, with the coalition now leading 52-48 on the two-party preferred vote, according to the latest Nielsen poll.
It's a six-point swing against the government during a week in which Prime Minister Julia Gillard's campaign was dogged by leaks.
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Speaking in Darwin, Mr Abbott said he expected the polls to go up and down.
"These polls are very volatile," he told reporters on Saturday, after announcing $77.5 million in defence health spending.
"I am very much the underdog in this election campaign."
Ms Gillard is still leading Mr Abbott as preferred prime minister in the poll, but her 21-point lead plummeted by 13 points to 49-41.
The polls were published on Saturday, as news of another cabinet leak emerged, this time on the issue of national security.
As deputy prime minister, Ms Gillard sent her bodyguard, Andrew Stark, to attend cabinet's national security committee meetings on her behalf, News Ltd reported.
The opposition is demanding her attendance record, along with that of former prime minister Kevin Rudd, who reportedly skipped several of the meetings as well.
Mr Abbott says "there's no heavier responsibility" than the meetings.
"Without the prime minister it's not possible to have an effective meeting ... and you could hardly have a meeting without the deputy prime minister either."
Mr Abbott said he "missed very few cabinet meetings" when serving in the former Howard government.
His deputy, Julie Bishop, said the prime minister can't "hide behind" the confidentiality of cabinet.
"Just who was in charge of national security in the Labor government," Ms Bishop, who is also opposition foreign affairs spokeswoman, told Sky News.
Labor frontbencher Craig Emerson defended Ms Gillard's decision not to comment.
He said leaks happen and Ms Gillard has so far handled them with "strong resolve", referring to reports earlier this week that she questioned the affordability of Labor's paid parental leave scheme and age pension hike.
Labor is ready for anything put in front of it during the election campaign, Dr Emerson said.
"Robbie Deans will say tonight to the Wallabies, you have to play what's in front of you," he told reporters in Canberra, referring to Australia's rugby team.
"And we play what's in front of us."
Ms Gillard is in Perth where reporters quizzed her on both the polls and the leak.
