Labour's deputy leader urged the party to "hold its nerve" in what would be a "dirty, vicious" campaign in 2015.
She dismissed talk of a possible future coalition with the Lib Dems, saying Labour was "not fighting for a draw".
While David Cameron and Nick Clegg "wallowed in complacency" over the recovery, Labour was "giving people hope their lives can be better".
By unveiling initiatives on energy, childcare, housing and training over the past four days, she said Labour had moved "from a party of protest, which understands people concerns, to a party of policy, which address those concerns".
She urged the party to build on this "momentum" by taking the fight to their opponents, saying Labour now had more active party members than the Tories and Lib Dems combined.
Ms Harman turned her fire on the Lib Dems, saying the party "had a nerve" to suggest it had acted as a restraint on their Conservative partners in government.
"They call it coalition. We call it collusion."
Referring to Nick Clegg's own conference speech last week advocating the merits of coalition, she suggested the deputy prime minister wanted "to go on and on and on and on" in office.
"Labour is not fighting for a draw. Labour is fighting to win."
Labour, she added, was the only party that truly represented women in the UK, suggesting prominent female figures were an "endangered species" in the other parties.
Harriet Harman has closed the Labour conference by saying election victory is "there for the taking".