SEOUL, June 2 (Reuters) - South Koreans elect new local representatives on Wednesday in elections widely seen as a barometer of President Park Geun-hye's response to a ferry disaster in April that killed more than 300 people, most of them children from the same school.
The sinking of the Sewol has sidelined traditional campaign issues such as jobs, education and welfare, and instead focused voter attention on a fierce national debate over the government's failure to enforce oversight on safety.
"This election is going to start with the Sewol and end with the Sewol," said Kim Hyung-joon, a political science professor at Myongji University in Seoul.
"It'll be favourable to the opposition and considerably disadvantageous to the ruling party."
Park's approval ratings fell sharply from 61 to 46 percent in the days after the disaster - her lowest since coming to power in February last year - and show little sign of improving.
Opposition candidates look set to win key mayoral races in Seoul, neighbouring Incheon and Busan in the southeast, but Park's ruling conservative Saenuri Party is unlikely to suffer landslide defeats.
Polls by Gallup Korea in late May suggested more than 40 percent of voters still supported the Saenuri Party, while only 28 percent said they supported the main opposition party.
About 40 percent of voters in South Korea are over 50 and traditionally vote conservative - unlike younger voters who are less likely to vote at all.
The opposition has also been careful not to use the government handling of the disaster as a political tool when distrust of politicians across the board has increased.
The elections are the first nationwide poll since Park took office. Opposition liberal Mayor of Seoul Park Won-soon has a 10 percent lead over the conservative candidate, and is expected to hold on to his position, seen by some as a springboard to the presidency.
Policy towards North Korea, which has threatened a fourth nuclear test in violation of U.N. sanctions, has not emerged as a campaign issue.
The Sewol ferry sank on a routine trip south from the port of Incheon to the traditional holiday island of Jeju on April 16. More than 300 people, most of them students from the Danwon High School on the outskirts of Seoul, died.
The ferry was heavily overloaded, was travelling too fast on a turn and many of its crew abandoned ship as the children waited in their cabins as told. They paid for their obedience with their lives.
Park, tears rolling down her cheeks, formally apologised last month for the disaster but she has been hit hard by an angry nationwide outcry over the government's response and the slow and ineffective rescue.
She has vowed to overhaul government structures and improve safety oversight to guard against any recurrence of preventable disasters.
Prime Minister Chung Hong-won resigned over the government response to the sinking, in which it was first announced that everyone had been rescued.
Chung was booed and someone threw a water bottle at him when he visited grieving parents the day after the disaster. Park was also booed by some relatives when she visited a gym where families of the missing were staying.
In further bad news for Park, her appointed successor for prime minister was forced to withdraw his nomination following allegations he abused his position as a former Supreme Court Judge to benefit his private law practice.
When campaigning, many election candidates now wear small yellow ribbons on their clothes. Initially a symbol of hope for the missing passengers and crew, the ribbon has evolved into a symbol of mourning.
"We want politicians to put party interest and politics aside and meet and talk with the families of the ferry victims," said Kim Young-hoon, a lawyer representing the families of the dead.
"There's no ruling or opposition in this," he said. "We are not trying to shake the country but improve it. Please work together." (Additional reporting by Sohee Kim; Editing by Jack Kim and Nick Macfie)