TOKYO — After just three months in office, Prime Minister Naoto Kan of Japan faces a challenge from a scandal-tainted power broker within his own party in a leadership race that could hamper the government’s response to a debilitating economic slowdown.
The power broker, Ichiro Ozawa, 68, said Thursday that he planned to run against Mr. Kan for the presidency of the Democratic Party on Sept. 14, a position that would ensure his appointment as prime minister. Mr. Ozawa, who is credited with the Democrats’ rise to power last year, has been increasingly critical of Mr. Kan since the party lost ground in elections last month.
Mr. Ozawa’s challenge could bring upheaval to the Democrats just as Japan’s recovery from a painful recession shows signs of sputtering. Growth slowed to just 0.1 percent in the most recent quarter, and the strength of the yen has threatened to erode earnings at Japan’s exporters because it makes their products more expensive abroad and therefore less competitive.
“Although I am unworthy, I have decided to run in the leadership election,” Mr. Ozawa said.
In a thinly veiled censure of Mr. Ozawa’s old-school politics, Mr. Kan said Thursday, “We must first break down Japan’s political structure, then construct a new one together.”
A divisive figure, Mr. Ozawa could also bring more political uncertainty to a country that has had five prime ministers in three years.
The Democrats ousted the Liberal Democratic Party last August after a string of unpopular prime ministers finally compelled voters to reject the L.D.P., a party that had governed Japan for most of the past half-century. Yukio Hatoyama of the Democrats took office as prime minister in September, only to resign nine months later over a broken campaign promise to move a United States Marine base from Okinawa.
His successor, Mr. Kan, first appeared to be winning back popular support for the party, but he has seen his ratings nosedive after suggesting that Japan may raise its consumption tax to tackle its mounting public debt.
Mr. Ozawa, the leader of the Democrats from 2006 to 2009, was forced to step down over a political financing scandal just months before his party’s rise to power. The scandal still clouds his future. He remains under criminal investigation, and a citizens’ judicial panel is expected to rule on whether he will be indicted after the Sept. 14 vote.