The wife of Ghana's ex-leader Jerry Rawlings is shocked after being barred from contesting the December election, her spokesman has told the BBC.
Nana Konadu Rawlings was chosen last weekend as the presidential candidate of the National Democratic Party (NDP).
She defected from the ruling National Democratic Congress (NDC) party, although Mr Rawlings has not done so.
The election commission said her nomination papers had not been completed before the deadline.
The main challenger to President John Dramani Mahama is expected to be former Foreign Minister Nana Akufo-Addo, from the New Patriotic Party (NPP).
Mrs Rawlings' spokesperson Owusu Bempah told the BBC her disqualification was unfair.
"We suspect someone deliberately wanted her out of the race," he said.
She refused to speak to the media.
Electoral commission spokeswoman Sylvia Annor told the AFP news agency that "there were major errors on their forms and they could not meet the deadline to rectify them hence the disqualification."
"Portions of the nomination forms were not properly filled by the National Democratic Party," she said.
Analysts had said that Mrs Rawlings' candidacy could split the NDC vote.
Before his wife's disqualification, there was speculation about which party Mr Rawlings - who ruled Ghana for 18 years and launched the NDC in 1992 - would support.
On Monday, Mrs Rawlings said her husband would support her presidential bid.
He had previously attended an NDC meeting where President Mahama unveiled the party's election manifesto.
He praised Mr Mahama, who became president earlier this year following the death of his predecessor, John Atta Mills.
Mrs Rawlings challenged Mr Mills last year in a bid to get the NDC's nomination, but gained only 3.1% of the vote.