Mired by a string of political scandals and a sluggish economy, the ruling party of President Lee Myung-bak, who is barred by law from seeking re-election, had been widely expected to lose its National Assembly majority in the Wednesday polls.
With the ruling party expected to win 152 of the total 300 seats up for grabs in the parliamentary elections, however, the unexpected victory proved Park's political clout as the "Queen of Elections," a nickname she won since she has led the party into victory in neck-and-neck elections several times over the past decade.
For her own part, the victory gave Park a powerful fillip ahead of the presidential vote in December, analysts said. Since the terms of office for the parliament and the president are set to run four and five years, respectively, the two elections are being held in the same year for the first time in 20 years.
Park Geun-hye smiles after watching results of exit polls on April 11. (Yonhap)
Park, a daughter of the late former president, Park Chung-hee, has not thrown her hat into the ring yet for the presidential race but she has no meaningful rivals within the party.
"The election results solidified the status of Park Geun-hye as the best choice for the presidential election in December," Koh Seong-kook, a political analyst, told public broadcaster KBS.
The conservative Saenuri Party, formerly known as the Grand National Party, had been in an emergency mode after losing the Seoul mayoral race last October. Public polls showed that the conservative party rapidly lost public support, dimming prospects for the Wednesday elections.
In January, Park put her presidential ambitions at risk by assuming the party's post to lead the parliamentary election campaign, while criticizing the policies of President Lee.
The Saenuri Party has been hit hard by an unfolding scandal that Lee's government was allegedly involved in illicit surveillance of his critics.
But the gap between the ruling and the main opposition Democratic United Party (DUP) had narrowed significantly after newspapers reported distasteful comments made by Kim Yong-min, the DUP's popular candidate for Seoul's Nowon district, in 2004 when he appeared on an Internet radio program.
Despite the overall victory, the Wednesday polls also revealed Park's limited influence in Seoul and its neighboring areas, which house nearly half of the nation's population. The DUP and other minor opposition parties swept those areas.
In Seoul's Jongro and Jung districts, for instance, two pro-Park heavyweight candidates, Hong Sa-duk and Chung Jin-suk, failed to win seats.
"Seoul and its neighboring areas are important for general elections as well as presidential votes," said Bae Jong-chan, a senior analyst at Research & Research, a polling agency. "The limited influence in the areas is a task that she must overcome to smoothly navigate through the presidential race."
The 60-year-old Park, whose mother was assassinated in 1974 by a North Korean agent unsuccessfully targeting her father, has expressed her willingness to engage North Korea more than President Lee. She also backed tax cuts for businesses to boost investment and create jobs.
This week's polls were also a dry run for other presidential hopefuls, including Moon Jae-in of the DUP and Ahn Cheol-soo, a popular college professor who often overtook Park as the top choice in public polls of potential candidates.
Moon, former close aide to former liberal president Roh Moo-hyun, won the crucial Sasang constituency in Busan, but other districts in the traditionally conservative Busan, the nation's second-largest city, were dominated by the Saenuri party.
Ahn had mostly remained silent, but posted a YouTube video clip two days before the vote, saying he would sing and dance in a mini-skirt if the voter turnout was over 70 percent.
High turnout, particularly from Internet-savvy young voters, was seen as a key asset for the main opposition party. The final voter turnout was 54.3 percent.
Ahn, founder of the nation's top anti-virus software firm, has no experience in politics, but his political influence was amply proven in the Seoul mayoral election last October. During the mayoral poll, Ahn merely voiced support for Park Won-soon, an anti-government independent candidate, but never campaigned for him. But that was enough to get him elected.