Soon after taking office two years ago, Mr. Lee appeared at risk of losing public support, as he faced mass demonstrations on the streets of Seoul against the import of United States beef. Now, political experts are talking about the “Cheonan effect,” as polls show that more than half of expected voters approve of the president and his tougher line toward the North.
Nowhere is the current upwelling of popular support more apparent than in polling for the local elections to be held across South Korea on Wednesday. Mr. Lee’s Grand National Party, whose candidates once faced tight races in some districts, now appears poised to sweep the most important races, including hotly contested mayoral elections in Seoul and the nearby port of Incheon.
Kim Moon-soo, the conservative governor of a province outside Seoul, just two weeks ago was in an uphill battle for re-election against a liberal opponent. Now, polls show him with a comfortable 15 percentage point lead.
“The only way to secure national security is to vote Grand National Party!” Mr. Kim recently told a crowd of flag-waving supporters, many of whom wore the sky blue of the governing party.
Such colorful displays are typical of the feisty and contentious election campaigns in South Korea, one of Asia’s most robust democracies. But the emotions unleashed in March by the sinking of the Cheonan, which killed 46 sailors, made what would have been local elections fought over public works and school lunches into an important national referendum on South Korea’s stance toward the North.
Politicians and political analysts agree that voters decisively turned to the Grand National Party after the announcement on May 20 of the results of an international inquiry into the sinking that found North Korea responsible. Political analysts said the results were enough to persuade many undecided voters to swing to the conservatives, who are seen as stronger on defense.
“The Cheonan is having a huge effect by pushing voters to rally around the flag,” said Kim Ki-shik, a political analyst at the People’s Solidarity for Participatory Democracy, a policy research group.
A telephone poll of 800 likely voters conducted Saturday by the East Asia Institute, a political research group, found that 52 percent of respondents approved of Mr. Lee in May, up from 46 percent a month earlier. It also found that 54 percent of respondents would “take the Cheonan into consideration” when casting ballots on Wednesday.
Political analysts said the sinking also soured many of these swing voters against the liberal opposition, which favors resuming engagement with North Korea, and which had been openly skeptical about whether the North was behind the attack. Some on the left have accused the president of manipulating the inquiry’s results to enhance his party’s chances in the elections.
But commentators warn that this wave of anger over the sinking does not signal unconditional support for Mr. Lee. In particular, they say that a majority of voters are against an openly confrontational stance toward the North, much less military retaliation.
In fact, after years of rising living standards and lowered tensions with the North under Mr. Lee’s two liberal predecessors, most South Koreans do not have the stomach for an actual standoff, political analysts say.
This means Mr. Lee must tread carefully, even as he stands with his nation’s closest allies, the United States and Japan, in calling for a firm response to the sinking. If he is seen as provoking North Korea, or pushing it too far, public sentiment could easily swing against him, analysts say.
“Voters are furious at North Korea now,” said Yoon Hee-woong, director of research at the Korea Society Opinion Institute, a polling company, “but the consensus here is clearly against confrontation.”
Mr. Lee’s current stance is that South Korea is willing to resume dialogue with the North, but only after it apologizes for the sinking and brings those responsible to justice.
At a speech in Bucheon, a suburb about an hour from Seoul, Mr. Kim, the candidate for governor, criticized the North for the attack. He did not call for revenge, but instead said that South Korea needed to bolster its own defenses and give moral support to the president in a time of crisis.
“Is this election about judging Lee Myung-bak?” he asked about 500 supporters outside a train station. “Or do we need to judge North Korea and Kim Jong-il?” he added, referring to the North Korean leader.
The supporters of his opponent, Rhyu Si-min of the People’s Participation Party, grouse that the sinking of the Cheonan had hijacked the elections.
“The Cheonan has crowded out all the other important issues,” said Mr. Rhyu’s chairwoman for campaign strategy, Kim Hyun-mee.
In Ilsan, a nearby city, Mr. Rhyu repeated in a hoarse voice his support for “peaceful coexistence” with the North.
Among his supporters at the rally, most of them in their 20s and 30s, suspicions run deep against the president and the United States, South Korea’s longtime protector.
“I don’t think North Korea did it,” said Lee Soo-hong, 39, who said he was between jobs. “I think the United States is using this incident to control South Korea.”
Mr. Kim, the conservative candidate, said that his party’s tradition of closer ties to Washington was helped him with voters.
“When people feel insecure, they feel the necessity of the United States,” said Mr. Kim, who paused before adding, “and the Grand National Party.”
Su-Hyun Lee contributed reporting.