Gerald Curtis, a political science professor at Columbia University, has closely followed Japanese politics for over four decades. But this year, he said, he has seen something extraordinary: "It has been never easier" to predict the results of this month's Upper House election.

"There is no way that (the ruling) Liberal Democratic Party will not enjoy a huge victory in this election," Curtis told reporters Monday in Tokyo at the Foreign Correspondents' Club of Japan.

Because of the "virtual implosion of (the) political opposition," voters have no credible alternative parties to support in a national poll for the first time in postwar history, he said.