Lawyer Titus Mvalo, who is representing Chakwera, the second petitioner in the case, told local media that the decision to drop the President was arrived at after assessing the evidence they have.
He did not elaborate on the evidence and why there has been this sudden change.
Mutharika, who was declared winner with 1,940, 709 votes against Chakwera’s 1,781,740 votes, is the second respondent in the case, while MEC is the first respondent and is being represented by Attorney General Kalekeni Kaphale.
The Chakwera decision comes a few days after the first petitioner, Saulos Chilima of UTM, who wants to have the presidential results nullified, dropped 34 witnesses from the case, after presenting only four, including Chilima himself.
A lawyer for Chilima claimed the decision was to expedite the case, which has gripped local and international attention as the opposition claim MEC rigged the election in favour of Mutharika.
MCP now says they have 19 witnesses.
But Frank Mbeta, lawyer for Mutharika, said it was impossible for Mutharika to be forced to appear before court, asking how you ask a respondent to give evidence for their case.
He said MCP made an allegation that Mutharika rigged the vote, saying it was the MCP itself which must prove the allegation.
The Mutharika team will parade 42 witnesses while MEC says it has 700 witnesses.
Chakwera is expected to start testifying in the constitutional court sitting in Lilongwe from Tuesday.
Chilima and Chakwera claim that Mutharika won a “fraudulent May 21 presidential election fraught with irregularities as there was alleged tampering with election results sheets with correction fluid called Tippex.
The historic case is expected to end in December and will cost over K200 million of government funds to run it.
A panel of five high court judges is hearing the case under tight security.