Presidential hopefuls of the ruling Saenuri Party on Saturday kicked off a one-month official race that will determine the party's nominee for December's presidential election.

Former party chief Park Geun-hye is considered a near-unrivaled favorite in the five-way race that also includes Gyeonggi Province Governor Kim Moon-soo, former South Gyeongsang Province Governor Kim Tae-ho, former presidential chief of staff Yim Tae-hee and former Incheon Mayor Ahn Sang-soo.

Party spokesman Kim Young-woo pledged in a statement his party will conduct a "fair election," and asked the candidates to compete with policies.

The race is expected to be closely watched for a possible alliance between the four candidates competing against Park, as they seek to boost their chances against her.

During the race, the aspirants will hold 10 joint speech sessions, six television debates and three policy debates.

On the first day of the official campaigning on Saturday, Park and Ahn concentrated on preparing for the debates and speeches, while Lim visited art museums in Seoul to meet with art industry officials over ways to boost the sector, according to their respective aides.

Kim Tae-ho visited a Marine base in Gimpo, west of Seoul, to meet with military personnel and tour front-line guard posts, his aides said.

Meanwhile, Kim Moon-soo started his campaign by visiting a site for a medical complex in North Chungcheong Province, and met officials there to discuss current issues in the science and technology sector, his aides said.

The Saenuri Party is scheduled to nominate its standard-bearer at a national convention on Aug. 20.

President Lee Myung-bak is scheduled to step down in February at the end of a single five-year term, and by the Constitution, he can't seek re-election (Yonhap).