The surprise resignation of Makiko Tanaka from the Lower House means more problems for the ruling Liberal Democratic Party, already facing an uphill battle in key Diet by-elections in October.

With Tanaka's resignation, there will now be six by-elections on Oct. 27. They will fill the voids in the Niigata No. 5, Yamagata No. 4, Kanagawa No. 8. and Osaka No. 10 districts of the Lower House, plus the Chiba and Tottori constituencies of the Upper House.

The LDP has thus far only been able to decide on a candidate for the Chiba election.

Preparations for the local campaigns are making little progress as the party continues to suffer from a series of financial scandals involving its members. Some LDP lawmakers warn that the party could lose all of the elections -- a result that could be devastating for Prime Minister Junichiro Koizumi.

Four of the six by-elections are being held to fill seats vacated by lawmakers who resigned over financial scandals during the last regular Diet session.

The four are former LDP Secretary General Koichi Kato of Yamagata, House of Councilors President Yutaka Inoue of Chiba, Kiyomi Tsujimoto, a member of the opposition Social Democratic Party, of Osaka, and Tanaka of Niigata.

The other two by-elections will fill a seat vacated by Hiroshi Nakada and a seat left open by the death in April of Shigenobu Sakano from Tottori. Nakada became mayor of Yokohama after voluntarily quitting as a Diet member from Kanagawa.

Lawmakers who voluntarily step down are barred from running in the by-elections to fill their vacancies.

Following Tanaka's surprise resignation on Friday, senior LDP leaders hurriedly launched an effort to find a candidate who can retain the party's reign in the Niigata district.

Although the LDP suspended Tanaka from party membership for two years in June over a scandal involving state-paid salaries to her aides, the party's leadership appears set to rely on her family by possibly fielding her son in the October race.

On Friday, LDP Deputy Secretary General Nobutaka Machimura telephoned Osamu Takatori, chairman of the party's Niigata prefectural chapter, to start arrangements to select a candidate for the by-election.

According to LDP sources, the prime candidate on party leaders' mind is Tanaka's eldest son, Yuichiro, 31, a certified accountant.

Even though Tanaka resigned in disgrace over the salary scandal, the Niigata constituency has been dominated by the Tanaka family since the days of her late father, former Prime Minister Kakuei Tanaka. In the last general election, in 2000, Tanaka defeated her runnerup by a huge margin of nearly 90,000 votes.

"Only the son Yuichiro's name is mentioned among LDP members in the Niigata chapter," said a senior party official in charge of campaign affairs. "Executives of local firms owned by the Tanaka family say they will strongly support his candidacy because they do not want Makiko to return to politics," he added.