The only political party that had supported Qadri's demonstration, the Mutahida Qaumi Movement, withdrew that support last week. The movement is a coalition partner in the current government.
If this year's elections take place without major difficulties, it would represent the first time in Pakistan's history that a civilian government would have made it through a five-year term.
Supporters say that Qadri aims to effect positive change.
Corruption is widely considered a chronic problem in Pakistan's political system; President Zardari has served prison time on corruption charges.
The problem appears to be regional. Qadri's campaign comes more than a year after anti-corruption demonstrator Anna Hazare roiled Indian politics with a hunger strike that called for the introduction of strong anti-graft measures.
Qadri gained worldwide attention in 2010 when he declared a fatwa, or religious ruling, on terrorism and said it "cannot be permissible in Islam."
That occurred during his time in Canada, when he spoke out in videos and books.
His supporters also point to his Lahore-based religious welfare organization, Minhaj ul Quran, which promotes "true Islamic teachings."
According to its website, it has up to 280,000 members worldwide and works to build schools around the country to teach the Quran.