For weeks, hard-line elements in Iran's government have been calling for the arrest of the country's opposition leaders, especially defeated presidential candidates Mir-Hossein Mousavi and Mehdi Karroubi. Now it appears that the government has raised the ante. On Sept. 8, Iranian authorities raided offices connected to the two men and arrested top opposition aides.In particular, Tehran appears to have targeted the opposition's ongoing strategy of charging the government with abusing the opposition demonstrators who were detained in the violence that followed Iran's contested presidential election in June. Security forces raided offices belonging to Karroubi — who has led the effort to collect evidence of abuse by security forces — and confiscated documents related to the charges.The raids are a measure of just how sensitive and damaging the claims of prisoner abuse have been for the Iranian government of President Mahmoud Ahmadinejad. Of all the charges leveled against his administration by opposition leaders since the election — including widespread electoral fraud and staging a coup d'état — none has been as sickly captivating to Iranians as the stories of abuse and torture that have trickled out from behind prison walls. Not only is sexual violence particularly abhorrent in conservative Iranian society, but the charges also challenge the legitimacy of the Islamic government by calling into question its foundation upon moral justice. The Islamic revolution was inspired in part by such abuse during the Shah's authoritarian rule.Though pressure from the rape and torture charges sparked a promise by Supreme Leader Ayatullah Ali Khamenei to bring any abusers to justice, the government is now, evidently, pushing back. A parliamentary committee that heard the evidence of abuse collected by the opposition summarily dismissed the charges last week, but two men who jointly presented the claims on behalf of the opposition — top Karroubi aid Morteza Alviri and top Mousavi aid Ali Reza Behesti — were arrested in the raids on Tuesday. The editor of Karroubi's website, which has also showcased the abuse allegations, was also arrested. The day before, authorities raided an office run by a Mousavi aide that recently said it had documented the deaths of 72 protesters in the weeks-long protests that shook the capital. (Authorities say 41 people, including security personnel, died during the prolonged crackdown after Ahmadinejad's disputed election victory, though human-rights groups put the number in the hundreds.)The latest crackdown demonstrates that the split between Iranian clerical leadership is only deepening, and how, despite the government's tight controls over public demonstrations, it remains wary of further dissent. The government has canceled or downsized celebrations for the Muslim holy month of Ramadan lest they become a platform for opposition protests. On Sept. 6, reformist former President Mohammed Khatami decried these and other "fascist" methods being deployed by the government. Just how much longer the government will allow opposition leaders to make such comments remains to be seen.