Yousuf Raza Gilani was disqualified as prime minister in 2012 after refusing a Supreme Court order to reopen an old corruption case against the president.
He was barred from holding office for seven years.
But that has not stopped him from campaigning for his Pakistan People's Party (PPP) reelection.
While the PPP wants to use the remaining two weeks of campaigning to highlight its record over the past five years, it is the recent return and subsequent arrest of the former military ruler Pervez Musharraf that has attracted the most attention.
In an interview with Al Jazeera, Gilani says he is pleased that Musharraf has been arrested.
"It’s a vindication. [Musharraf's government] gave the assurance that when [Bhutto will come] to Pakistan, she would be given full security, and that was not given."
Al Jazeera's Imtiaz Tyab reports from Multan.