The race for the upcoming Seoul mayoral by-election is all but set, with the ruling and opposition parties likely to finalize their candidates by the end of this week.

The competition has heated up with the addition of each new runner, the latest being former Seoul Mayor Oh Se-hoon, who declared his candidacy on the ticket of the main opposition People Power Party (PPP) on Sunday.

All eyes are now on the decision of Park Young-sun, minister of SMEs and Startups, who is widely expected to throw her hat into the ring later this week after President Moon Jae-in's Cabinet shakeup.

Once that is complete, the preliminary lineup for the April 7 by-election will most likely list two contenders from the ruling Democratic Party (DP) -- Park and Rep. Woo Sang-ho -- 10 candidates from the PPP, including Oh and former floor leader Na Kyung-won, and Ahn Cheol-soo, leader of the minor opposition People's Party.

The election bears a larger emotional significance compared to other by-elections, as it fills a vacancy left by former Mayor Park Won-soon, who was found dead in an apparent suicide in July following allegations of sexual harassment against a female secretary.

It also comes at a time when businesses are suffering under the constant strain of the coronavirus pandemic and citizens are growing increasingly frustrated with soaring housing prices in the country.

Not surprisingly, candidates are appealing to voters with new proposals to ease their financial burdens and promises aimed at stabilizing the housing market.

Woo, for example, has pledged to supply 160,000 new public housing units in the hopes that stabilizing public housing prices will also bring the private housing market under control.

The PPP, on the other hand, has promised to significantly deregulate the real estate market to encourage redevelopment projects and thus expand supply of homes.

Some DP officials have expressed hope that Park Young-sun's experience as SMEs minister will help her win votes.

Last week, the minister was seen meeting -- and at one point shedding tears -- with merchants at a traditional market. She said the visit was aimed at checking whether the government's COVID-19 relief funds were properly distributed.

Na has billed herself as the standard-bearer of the conservative opposition bloc, which has tried to make a national political comeback since the liberal administration under President Moon Jae-in took office in May 2017, following the impeachment of President Park Geun-hye. The PPP also suffered a crushing defeat in last April's general elections.

Oh, meanwhile, has made "atonement" and his prior mayoral experience a centerpiece of his campaign. In his speech on Sunday, he apologized to Seoul's citizens and his party for resigning midterm in 2011 and thus paving the way for Park Won-soon's election.

Oh stepped down as mayor after failing to block a free school lunch program led by the then opposition in the city's first-ever referendum.

The opposition's chances at winning the election will hinge on whether it can field a single united candidate to take on the ruling party.

Ahn, who gave up his candidacy despite leading the polls in 2011 to back Park Won-soon, has so far rejected the PPP's calls to join the party and compete in its primaries. Candidate registration for the party's primaries began Monday.

PPP interim leader Kim Chong-in told reporters last week that Ahn is left with two options: negotiate merging candidacies before candidate registration with the National Election Commission opens in early March, or join the PPP before then.

Meanwhile, Ahn has shown a strong lead in opinion polls.

In a survey conducted by WinGKorea Consulting from Jan. 2-3, Ahn beat Park Young-sun in a hypothetical two-way race with 47.4 percent of the vote against Park's 37 percent.

Oh gained 43.9 percent against Park's 38.7 percent, while Na garnered 39.8 percent against Park's 40.1 percent.

Ahn was also chosen as the most suitable opposition candidate by 28.5 percent of the survey's respondents, followed by Na (12.9 percent) and Oh (12.6 percent).

The survey had a margin of error of 3.1 percent at the 95 percent confidence level. (Yonhap)