An upstart presidential contender in Korea's ruling party launched a high-stakes campaign Monday to change the way the party selects its presidential candidate, a day after he announced a surprise bid for the top office.

Changing the rules in the ruling Saenuri Party's presidential primary could boost the chances of Gyeonggi Province Governor Kim Moon-soo, an underdog believed to be trailing way behind the party's leader and long-time presidential hopeful, Park Geun-hye.

Declaring he will run for president, Kim claimed Sunday that the party should not bask in precarious optimism that Park would prevail in December's presidential election, and that he stands a better chance to win the vote as he appeals more to younger voters than Park.

When it comes to the party's primary election, however, Kim's chances of beating Park appear slim. Park has broad support from across the party and the current primary rules appear favorable to her because they give roughly the same weight to party members and ordinary citizens.

Kim wants to change the rules to give ordinary citizens a greater say in the process.

In a radio interview Monday, Kim made a pitch for an "open primary" that selects the party's presidential candidate based entirely on support from ordinary citizens regardless of their party membership. Kim claimed that the current system fails to correctly reflect the views of the people.

"With a structure where views of the party are way apart from views of the public, we have no chances of winning the main race in which only views of the public will be taken into account," Kim said, referring to the December presidential vote.

Kim also stressed that the party's primary rules should be changed to have them correctly reflect the situation, rejecting claims from party members close to Park that the party should stick to principles and keep the current rules intact.

"Promises were made in the past, but the presidential election is coming up," he said. "It is dangerous to wipe out all future possibilities by repeatedly talking about what was done in the past."

But party members close to Park rejected Kim's demand.

"It doesn't make any sense to demand a change in the primary rules depending on the calculations of political advantage and disadvantage," a lawmaker said on condition of anonymity. Another lawmaker also accused Kim of attempting to "scar" Park.

Park consolidated her standing as a leading presidential hopeful of the ruling party after rebuilding the once-beleaguered party and leading it to an upset victory in the general elections earlier this month.

In a survey conducted after the polls, Park received 47.9 percent of support, compared with 44.8 percent for star software developer and science scholar Ahn Cheol-soo. The survey of 1,500 voters had a margin of error of plus or minus 2.53 percentage points.

Ahn surged as a potential opposition presidential contender after he demonstrated his powerful influence on voters during October's Seoul mayoral by-election. Afterwards, Ahn had led Park in popularity surveys for months. He lost his lead after the general elections. (Yonhap)