SEOUL, South Korea — Just a few months ago, Park Geun-hye was the president of South Korea. Now she is Inmate No. 503.

The daughter of a president who spent her youth in the presidential residence, Ms. Park ascended to the presidency herself four years ago. She now lives in a 114-square-foot jail cell as she awaits her trial on corruption charges.

Ms. Park, whose privileged upbringing and fastidiousness earned her the nickname Princess, once had the city of Incheon install a new toilet for her use during a presidential visit, according to the city’s former mayor. Now she eats $1.30 meals (paid for by the government), washes her own tray and sleeps on a mattress on the floor.

She can watch the television in her cell for up to six and a half hours a day. Its only channel plays programs approved by the government, including news, documentaries and soap operas, the plots of which could hardly be as unlikely as Ms. Park’s tumble from power.In December, lawmakers voted to impeach her, and she was formally removed from office on March 10. The charges against her include bribery, extortion and abuse of power.

Though Ms. Park has been living in the Seoul Detention Center since she was arrested on March 31, her name still stirs raw emotions among both her critics and supporters as the country prepares to vote Tuesday to elect her successor.

Many South Korean liberals and progressives view the election as another opportunity to discredit her and punish her conservative allies. Moon Jae-in, a political nemesis of Ms. Park, is favored to win the election, according to recent surveys.

But many conservatives still consider her to be innocent.

A small group of her supporters has been rallying in front of the jail in Uiwang, south of Seoul, every day. Police barricades and roadside trees were plastered with banners and slogans calling for her release.

“Dear President Park Geun-hye, we love you,” one read. “Please hang in there. We stand by you.”

Cho Won-jin, a minor conservative presidential candidate, began his campaign last month by kneeling in front of the jail house and bowing in Ms. Park’s direction.

Hong Joon-pyo, a conservative who is currently second or third in the polls, said that if elected, he would pardon her.

Mr. Hong roiled the campaign recently by saying that Ms. Park had fallen gravely ill, while Mr. Cho claimed that she was on a hunger strike.

“They should send her to the hospital,” Mr. Hong said. “But they don’t because they are afraid to displease Moon Jae-in.”

The claim went viral, forcing the government to deny that Mr. Park was on a hunger strike or ill. Her lawyers also denied the rumor.

Je Youn-kyung, a spokeswoman for Mr. Moon, said Mr. Hong was spreading “fake news” to woo conservative voters sympathetic toward Ms. Park.

Ms. Park’s trip from the presidential Blue House to the jail house is the most sensational political downfall South Koreans have seen in decades.

Ms. Park grew up in the Blue House; her father, Park Chung-hee, ruled South Korea from 1961 until his assassination in 1979.

She returned there in 2013 as president. She was impeached after four years. Now out of office, she is accused of collecting or demanding $52 million in bribes from businesses in collusion with a longtime confidante, Choi Soon-sil.

Ms. Park denies the charges.

Single and without children, Ms. Park, 65, has been estranged from her sister and brother for years. As president, she was accused of keeping her official presidential aides at arm’s length but allowing inappropriate access to a group of secretive friends including Ms. Choi.

But her days in jail may be her loneliest time.

The Korea Correctional Service, a government agency in charge of running prisons around the country, keeps a tight lid on information about Ms. Park’s incarceration. It is known that her solitary cell, bigger than others, is separated from the rest of the jail by a partition. Other inmates are not allowed to approach her.

She has allowed only three visitors: a former aide and her two lawyers, with whom she spends most of her time preparing for her May 23 trial.

If she is convicted of bribery and other charges in the coming trial, she could spend from 10 years to the rest of her life in prison.