The Turkish people are suffering from "power fatigue" and "polarization," presidential candidate Ekmeleddin Ihsanoglu told foreign media in Istanbul on Wednesday, Anadolu agency reported.
Claiming "people are looking for new leadership," he said: "I stand for democracy and secularism, and against the accumulation of totalitarian power.
"We are for multi-party transparent democracy and the separation of powers. We must establish justice so the supremacy of law returns. We must stop the interference of politics in law."
Ihsanoglu is viewed as the main challenger to Prime Minister Recep Tayyip Erdogan, who is standing in the August 10 poll for the ruling Justice and Development Party, and who is suspected of wanting to increase the power of the presidency.
Ihsanoglu added: "The president should not have his own political agenda. If the president, who is supposed to be impartial, interferes in politics, this leads to disaster.
"We should have serenity at the top of the state. The president should solve problems, not be a man who creates them."
Ihsanoglu is the former head of the Organization of Islamic Co-operation and was nominated as the opposition's joint candidate for the presidency last month. Among the 10 parties supporting him are the main opposition Republican Peoples' Party and the Nationalist Movement Party.
He said Turkey's foreign policy should be one of "cool, silent diplomacy" and, in a slight on Erdogan's involvement in Syria, "non-interference in neighbors' internal affairs."
Turkey should remain a partner with Europe and remain "firmly rooted in the Euro-Atlantic community," he added.
Turning to this week's arrests of senior police officers charged violated the privacy of government figures, including the prime minister and his close allies, Ihsanoglu called for "supremacy of law and respect for human rights."
He criticized Erdogan's use of government vehicles while campaigning, calling his use of an airplane and helicopter a "farce."
On the sensitive subject of the solution process with the outlawed Kurdistan Workers' Party, or PKK, Ihsanoglu told journalists: "As with any Turk, as with any citizen, I want peace. We are for the peace process and negotiations. My approach here is based on these points: We have 1,000 years of shared history and a shared homeland, we need improvement on human rights."