His family has been told he cannot be released until he produces a passport and collects signatures from various officials
President Yahya Jammeh seized power in a 1994 coup and has targeted opponents and several of his own ministers, while surviving multiple attempts to remove him from power.
In the months prior to the December 1 vote, a former minister, an ex-ruling party MP and two journalists with the state broadcaster are among those who have been detained, often without a clear reason.
Jainaba Bah said she still doesn't know why her husband, former junior foreign affairs minister Mamadou Sajo Jallow, has been in custody since early September and denied access to a lawyer.
"My personal view is that he has been arrested because I have declared my support for the UDP (opposition party)," she told AFP by phone on Saturday from Sweden.
Her husband, a longtime ambassador to the African Union in Addis Ababa, Ethiopia, was taken away by the security services on September 2 after his house was burgled and official documents taken.
But his family has been told he cannot be released until he produces a passport and collects signatures from various officials, tough conditions to meet while he is behind bars and his wife has fled to Sweden.
"I can't sleep," Bah said, describing the "whole range of things that might be possible from the stories I have heard about," referring to alleged abuses committed in The Gambia's notorious prisons.
Allegations of torture and rape, especially in Banjul's Mile Two prison, are common.
Isatou Touray, a leading women's rights campaigner and a member of the opposition coalition that is fielding a single candidate against Jammeh this election, says such arrests have become familiar.
"This has been the norm in the Jammeh regime. You can never predict whether a minister is going to be there for three months or even three days," she said at a rally in a village outside the capital.
"He is the alpha and omega of everything," she added.
Calls to the interior ministry by AFP about Jallow's case went unanswered on Sunday.
Those who opt to leave the government are also at risk, especially deputies who have joined the Gambia Democratic Congress, a grouping of mostly former ruling party officials.
Tina Faal, formerly of the ruling Alliance for Patriotic Reorientation and Construction (APRC), was detained for three weeks in August despite already being on bail over a separate theft case. No reason was given for her re-arrest.
"They told us that they have documents they want to hand over to her. But they did not disclose their identities to us," a family source told AFP at the time of the men that descended on her home.
Meanwhile most of the top officials from the leading opposition United Democratic Party remain in jail, serving three-year sentences for holding protests.
They were arrested while calling for political reform on April 14 or at a subsequent demonstration over the death of UDP official Solo Sandeng in custody.
Touray, the women's rights campaigner, believes this has galvanised huge street rallies observed across the country, unprecedented in a nation where political expression is discouraged.
"The people can no longer tolerate the human rights abuses and all the difficulties that they are facing," Touray said.
For young Gambians, the wave of arrests has only pushed some closer to a confrontation with the authorities.
"Our leader Ousainou Darboe was picked up just metres away," said one young man openly wearing a T-shirt of the opposition coalition near a mosque in Banjul.
"I am standing here, so many people will be worried about me. They will be worried I will be picked up but I don't care about that anymore."
President Jammeh told UN Secretary-General Ban Ki-moon to "go to hell" when he demanded an enquiry into deaths in custody in April, and has also described dying while being detained or during an interrogation as "really common".
Beyond the political sphere, journalists are also routinely arrested, with several detained during the sensitive weeks ahead of the election.
Momodou Sabally, the director-general of Gambia's state television and radio broadcaster, and his colleague Bakary Fatty were taken away earlier in November.
Sabally and Fatty broadcast images of the opposition when Jammeh's wife was due to appear, according to Human Rights Watch.
This week Sabally was charged with "economic crime", negligence of official duty, abuse of office and spreading false information.
The final charge, denounced as overly vague by rights activists, is often used against journalists.
Rights group Amnesty International has called for Sabally's release, adding that "all those detained for simply expressing their opinions should be freed without condition."