On the eve of the Seoul mayoral election, the rival candidates crisscrossed the capital city Tuesday to make last-minute pitches for support amid indications of a very close race. Wednesday\'s by-election pits Na Kyung-won of the ruling Grand National Party (GNP) against Park Won-soon, an opposition-backed candidate without party affiliation. Rival camps have thrown all their resources into the election in the past week in hopes of a win as the two candidates have been neck-and-neck in recent surveys. The election was set up as ex-mayor Oh Se-hoon stepped down in late August after he failed to downsize the opposition-led free school lunch program in a referendum. Na, 48, a former judge and two-term lawmaker, has accused Park of being a demagogue and hypocrite, raising allegations that he dodged the national mandatory military service and forged his academic record. Park denied the charges, criticizing the ruling camp of engaging in mudslinging. The 55-year-old Park, a lawyer-turned-activist, has received broad support from young and liberal voters. The political novice was picked as the unified candidate in a primary by opposition parties, beating a two-term lawmaker of the main opposition Democratic Party (DP). With the election entering its waning hours, the two candidates poured forth an all-out effort to drum up support. Na rode public buses and the subway around the city to meet citizens. She will join a large campaign rally with GNP leader Hong Joon-pyo later in the day, according to her camp. Park crammed his schedule with rallies, stopping by fish markets and night markets at dawn and meeting people in subway stations and busy districts. The by-election has drawn much attention as Park Geun-hye, the GNP\'s leading presidential hopeful, has hit the campaign trail on behalf of Na, a move seen as indication that she is gearing up for her second bid for the presidency. The 59-year-old Park has so far taken a hands-off approach in party affairs and elections amid soured relations with President Lee Myung-bak after she lost to Lee in the party\'s 2007 primary to select a presidential candidate. In the loosely united opposition camp, popular software entrepreneur Ahn Cheol-soo openly backed the liberal lawyer, showing up for a media briefing and delivering a letter of support on Monday. The media-shy IT mogul, who is widely popular among young and neutral voters for his clean and upright image, stunned the main political parties when opinion polls showed him as the most preferred choice for the presidency even after he gave up his mayoral bid and threw his support behind Park. With Ahn\'s backing, Park, then a lesser-known activist, saw his single-digit approval ratings rise to the top. Apparently mindful of Ahn\'s impact in the polling results, Na criticized her rival of relying on outsiders to win the race. \"It proves that (Park) is neither qualified nor able to become mayor without the help of Prof. Ahn,\" Na said in a radio interview. The ruling conservatives attacked the independent candidate, saying his shaky political grounding would cause confusion in city affairs. \"Politicians should be held accountable, but independent candidates do not take responsibility even if there are problems,\" GNP floor leader Hwang Woo-yea said. \"Supporting the independent candidate would not help any responsible politicians, but would rather create confusion.\" Park called on voters to make their own judgment to bring a fresh change, not base their decision on the \"massive negative campaign\" by his rival. \"Only one day is left before the battle,\" Park said. \"Do you want a change or just another version of ex-mayor Oh Se-hoon?\"