As is often the case with presidential elections, it may not be party loyalists and ideologically committed voters that will have the final say this time. Instead, it is a small number of swing voters that will probably hold sway in a closely contested race on Wednesday.

Of course, this is not to say that the vote of each party’s loyal supporters is of little significance. On the contrary, a large voting bloc in favor of a party is a prerequisite when the party enters a presidential contest. As shown by the case of the Unified Progressive Party, it is hardly thinkable for a sane political group to make it to the finish line when it does not have a strong power base.

But it is equally true that support from a traditional voting bloc is not enough for either Park Geun-hye of the conservative ruling Saenuri Party or Moon Jae-in of the liberal opposition Democratic United Party to win the election. The reason is that the race is thought to be too close to call. Given that the gap in approval ratings between the two contenders is believed to be within the margin of error, swing voters are destined to hold the casting vote in this election, as they have often done in the past.

Park had led Moon in opinion polls, mostly within the margin of error, until the outcomes of surveys conducted after Dec. 12 were banned from being made public. The Dec. 12 surveys showed that Moon had been fast catching up with Park, rendering it difficult to predict who would win the race.

The gap ranged from 0.1 percentage point in a survey commissioned by The Korea Herald (47.8 percent for Park and 47.7 percent for Moon) to 6.8 percentage points in a poll commissioned by SBS (48.9 percent for Park and 42.1 percent for Moon). Almost all polls indicated the gap had been narrowing fast ― by as much as 4.8 percentage points in a week, as was shown by the Korea Herald survey.

The shift in voter sentiment started when the independent Ahn Cheol-soo bowed out of the race late last month, pledging his support for Moon. Now the question is whether or not Park has arrested the change before it could threaten her victory.

Another setback for Park was the recent withdrawal of Lee Jung-hee of the United Progressive Party. Lee’s approval ratings had been less than 2 percent, but should her supporters vote for Moon, as she urges, Moon’s aides believe it could possibly mean victory for him.

Her influence was something to be reckoned with if an estimate, made prior to Lee’s withdrawal by one of Moon’s top election strategists, was correct. A co-chair of Moon’s election committee said a difference of 100,000 to 300,000 votes would seal the fate of a candidate.

The number of people that had wanted to vote for Lee would range from 280,000 to 560,000, assuming that 70 percent of the 40,464,641 eligible voters decide to go to the polls and that 1 percent to 2 percent of them were perceived to be her loyal supporters. These people, if mobilized to vote for Moon, would pose a serious threat to Park’s win.

Another group of eligible voters that are assumed to have a great influence on the election outcome is the undecided. According to surveys conducted on Dec. 12, about 10 percent of voters were still undecided.

It is anyone’s guess how many of them will turn out to vote. But a senior official of the Saenuri Party was ill-advised when he said it was his party’s strategy to discourage them from voting. He was apparently worried that many of them would eventually decide to vote for Moon.

Equally misguided was a top official of the Democratic United Party when he made a disparaging remark about aged voters, whose voting behavior he believed to be skewed in favor of the conservative ruling party.

Both parties should be reminded that to vote is not just a right for a citizen but his responsibility. As such, all eligible voters should be encouraged to go to the polls. It goes without saying that the undecided will have to exercise prudence in making a final decision who to vote for.