Al-Jubouri was the third candidate from the party to be killed in the past two weeks.
A police source, who asked not to be named, said al-Jubouri was shot dead by gunmen in police uniform.
He said the men searched several homes in al-Jubouri's village saying they were looking for mortars.
On entering his home, "they tied up his brother and when he came downstairs they opened fire and killed him," he told the Reuters news agency.
The Iraqiya party says al-Jubouri was killed for political reasons.
Maysoun Damlouji, the spokeswoman for Iraqiya described the attack as one in a string of killings "clearly targeting the Iraqiya list".
Two other Iraqiya candidates were gunned down in February and May.
"Iraqiya was targeted before the election, and the attacks are continuing," Intisar Allawi, a senior Iraqiya official, told Reuters.
"We don't know who we will lose next. We call on the government to provide protection for winning candidates."