Nasa on Tuesday said President Uhuru Kenyatta had conceded defeat following his declaration that Jubilee would impeach the coalition's flagbearer Raila Odinga if he wins the repeat poll.
Speaking during a rally in Kibra, Nairobi, Mr Odinga said the remarks by the President showed desperation after Jubilee rigged the August elections.
Mr Odinga -- who led his co-principals Kalonzo Musyoka, Musalia Mudavadi and Moses Wetang'ula in the campaign -- said the tyranny of numbers enjoyed by Jubilee in both the National Assembly and the Senate is as a result of the rigged polls.
"The IEBC (Independent Electoral and Boundaries Commission) stole the elections, from the presidency all the way down to the MCA seats," Mr Odinga said.
"The numbers Jubilee is bragging about are products of the sham elections," he added.
Mr Wetang'ula said: "We want to thank Mr Kenyatta for conceding defeat in favour of Mr Odinga but warn him that the Constitution is very clear on the grounds on which a president can be impeached."
Mr Mudavadi warned that Mr Kenyatta's remarks could result in a reversal of the freedoms stipulated by the Constitution.
"The statements by Mr Kenyatta were reckless and a mark of an authoritarian regime," Mr Mudavadi said.
President Kenyatta on Sunday said Jubilee lawmakers would impeach Mr Odinga should he win the October poll since it commands a solid majority in both Houses.
On the fundraising, Mr Odinga defended the move by the National Super Alliance to raise campaign funds from supporters through M-Pesa, saying this was legal.