President Uhuru Kenyatta introduced a twist in the State House race when he said Jubilee MPs would impeach Mr Raila Odinga should he win the election.
Jubilee commands a solid majority in the National Assembly and the Senate.
In a rejoinder, the National Super Alliance said the President’s threat was an act of desperation.
Nasa principal Moses Wetang’ula questioned the basis for such a decision.
“It clearly shows how ill-informed the President is about the constitutional provision and the level of desperation he is showing by pressing every panic button before going to the repeat election,” the Bungoma senator told a press conference.
The President was addressing leaders from Machakos, Makueni and Kitui counties who promised to support his re-election bid.
Mr Kenyatta wanted to know how Mr Odinga would lead the country, “considering that we have the majority of MPs and senators”.
He said the numbers could be made bigger should affiliate parties and independent candidates throw their weight behind Jubilee.
He said with slightly less numbers in the 11th Parliament, determined Jubilee-friendly MPs pushed through legislation under chaotic circumstances.
“In the last Senate, we could not pass Bills because we were evenly balanced. Today, we can do business in the Senate without a Nasa member present.
"We don’t need them. We are only 13 members shy of a two-thirds majority in the National Assembly. We can even change the Constitution,” he said.
“There is no need to fear even if he is elected. We have the opportunity within three months to impeach him.
"If you splash the billions of shillings to be spent in the repeat election that could be used for development on him, what is he going to do?”
The Constitution says a president can be removed from office on grounds of incapacity.
An MP supported by at least a quarter of parliamentarians may move a motion to investigate the president’s physical or mental capacity to perform the functions of the office.
If the motion goes through, the Speaker writes to the Chief Justice informing him of the resolution.
The CJ then appoints a tribunal, which investigates and reports the matter within 14 days.
The report is final and not subject to appeal. If it finds that the president is incapable of running the office, the National Assembly votes on whether to ratify it.
If a majority of MPs vote in favour of ratifying the report, the president ceases to hold office.
The Constitution also says the National Assembly may pass a motion to impeach the president but it must be supported by at least a third of the members.
It cites reasons for a presidential impeachment as gross violation of the Constitution or if the head of state has committed a crime.
If the motion is supported by at least two thirds of the MPs, it is sent to the Senate, which must decide if the allegations can be substantiated.
The National Assembly may appoint a committee to investigate the reports.
The president has the right to appear and be represented at the special committee during the investigations.
The Senate then considers its report, and may not proceed if the claims cannot be justified.
If the committee reports that allegations are justified, the Senate decides whether to vote to uphold the charges.
Nasa dismissed the President’s threat, saying there would be no reason to warrant the impeachment of a Raila presidency.
“What charges would be levelled against Raila? That is a reckless speculation that is not consistent with the conduct of a President,” Mr Wetang’ula said.
Mr Kenyatta also dared Nasa lawmakers to make good on their threat to skip the first sitting of 12th Parliament.
“Well done. Boycott! We have prepared the Bills. We want to dust and then pass them. If they refuse, what is the problem?” he asked.