Read this and this and then read this. There is no direct evidence of Iranian involvement in these assassinations, but the question must be asked in light of the NCRI’s reporting. A female MP of the al-Iraqiya list was just targeted for murder, perhaps uncoincidentally at the same time as Maliki is opening the door to allow Allawi to become PM, surely enraging Iran and its political allies in Iraq.
The newspaper report notes that three members of the al-Iraqiya bloc have been killed since the campaign began. As written here, there’s been several other attempted assassinations and those are only the ones we know about.