Iran police use tear gas, clubs to crush protest. As a general rule of thumb, the use of tear gas represents an escalation in police response. Tear gas means you’re serious.
The street protests appear to have been largely crushed, but the opposition has vowed to continue pursue “legal challenges” to the election.
I’d say those legal challenges will get them exactly nowhere. If that’s all they’ve got left then it’s game over.
Update: On the other hand, Edward Luttwak in the Wall St Journal thinks that it’s over for the regime, not the protestors:
At this point, only the short-term future of Iran’s clerical regime remains in doubt. The current protests could be repressed, but the unelected institutions of priestly rule have been fatally undermined. Though each aspect of the Islamic Republic has its own dynamic, this is not a regime that can last many more years.