Labor candidate Maxine McKew has blamed the loss of her NSW seat of Bennelong on the government's failure to live up to its promises on emissions trading and the sudden ousting of former prime minister Kevin Rudd.
She also pointed to voter cynicism over a $2.6 billion election pledge to build a rail line linking the northwest federal electorate and Sydney's western suburbs.
Ms McKew conceded defeat soon after the Australian Electoral Commission called the seat for the Liberals' John Alexander on Saturday night, saying it was a big disappointment for the party.
"A lot of the class of 2007 have lost their seats and of course I am among them - I was on a wafer-thin margin," she said.
"It's particularly tough because people here tonight fought the good fight in 2007 and of course we claimed a historic victory.
"But we have not been able to prevail tonight, so yes, it's extremely disappointing."
A smiling and graceful Ms McKew reasoned that her re-election chances were harmed by the dumping of Mr Rudd in June.
"Well, you cannot have a Labor leader removed within two months of an election for it not to have significant ramifications, so clearly that was a factor," she told the ABC.
But the government had also failed to properly claim its victory during the global financial crisis, and voters had also lost faith in the government when it walked away from the carbon pollution reduction scheme, she said.
"The disappointment, with the kind of government we said we would be, I think has been acute," she said.
However, Labor's $2.6 billion promise to build a 14km direct rail link between Parramatta and Epping in partnership with the unpopular NSW state Labor government was also a factor.
Asked if she thought the transport pledge, announced by Prime Minister Julia Gillard and NSW Premier Kristina Keneally, had counted against her, she replied: "I think you might be right".
"There was a lot of cynicism," she told the ABC.
"I think given the on-again, off-again nature of transport commitments in this city, we are battling uphill to convince people of the credibility of that commitment."
Mr Alexander, a former professional tennis player and commentator, squarely blamed Ms McKew's loss on the proposal.
"The Parramatta railway line, that was seen as such a transparent and insincere gesture," he told reporters.
"It was a hollow promise from a desperate person trying to buy five marginal seats."
At the 2007 election, Ms McKew famously ousted sitting member and prime minister John Howard, who had held the seat since 1974.
She won the seat on a margin of just 1.4 per cent.
But with 78 per cent of the votes counted by late Saturday, Ms McKew had a 5.2 per cent swing against her, paving the way for the Liberals to snatch back the seat.
Mr Alexander denied he was a coalition "giant slayer", saying he admired Ms McKew.
"I don't think it is like that at all," he told reporters.
"This has been a very hard-fought campaign."
Asked if she had any regrets, Ms McKew said she had none, and that she'd "do it again tomorrow".
"I knew what I was in for and I thought it was important to run for a marginal seat.
"It's been a privilege and a joy."
