TOKYO, Aug. 10 (Xinhua) -- Former Defense Minister Shigeru Ishiba officially declared his candidacy on Friday for the ruling Liberal Democratic Party's (LDP) leadership race next month.

Ishiba, 61, a lower house member, has in the past been outspoken about Prime Minister Shinzo Abe and his policies and this will be the third time the veteran politician will attempt to win the ruling party's top post.

While Abe has yet to officially declare his candidacy, he is widely believed to win his third three-year term as LDP President and in doing so becoming the longest-serving prime minister.

But Ishiba, who has the support of a powerful LDP faction and has held key posts in the party including defense minister, LDP secretary general and minister in charge of revitalizing local economies, may be able to take advantage of slumping support rate for Abe and his Cabinet following a slew of cronyism and document tampering scandals.

While many believe Abe's success will be a foregone conclusion, some believe that Ishiba's "honest and fair" politics may for some be a refreshing change from Abe who has long been caught up in cronyism scandals.

Ishiba has also been a vocal critic of Abe's plans to revise Japan's Constitution and actually rewrote his own constitution revision proposal in February.

While acknowledging some of the positives of "Abenomics", Ishiba is a proponent of introducing more methods to bolster regional economies.

In light of the government's tardy handling of a spate of recent natural disasters, Ishiba has proposed to set up a new ministry dedicated to taking charge of disaster prevention.

The LDP presidential election, which will also effectively decide Japan's next prime minister, is slated to be held on on Sept. 20, with official campaigning starting on Sept. 7.