Three weeks of protest have taken a political toll on Turkey’s prime minister that could upend key parts of his political agenda, including his ambition to rework the constitution and emerge as Turkey’s most powerful leader in its democratic era.

Recep Tayyip Erdogan’s vehement stance against the protesters and the political opponents he accuses of helping them has polarized the country — and shrunk a broad support base that extended well beyond his core religious voters. His crackdown is also damaging a key political asset: His image as a statesman who strengthened Turkey’s role on the world stage and engineered its economic boom.

Erdogan’s weakened position could be an opening for others in his party who have long stood in his shadow, including President Abdullah Gul. Meanwhile, the prime minister’s struggles may make him a less reliable partner for the West at a time when its leaders are navigating difficult issues on Turkey’s border, such as Syria’s civil war. Turkey’s turmoil is also a blow to the nation’s already waning chances of joining the European Union.

Erdogan has been seeking constitutional changes that would strengthen the powers of the presidency and allow him to shift into that role after elections in August 2014. But the changes require a parliamentary supermajority, which his party does not command. It once looked likely that Erdogan could pass the changes with help from a smaller Kurdish party, but that potential ally is unhappy with his recent nationalistic turn. And the political upheaval may even limit votes within his own party.

Meanwhile, Erdogan has attracted widespread criticism from abroad over his hardening authoritarianism, particularly from Europe and the United States. In the most tangible setback, European leaders are wavering about talks planned later this month on Turkey’s slow-moving bid to for EU membership.

“If you look back at the last 10 years, Erdogan and his party enjoyed enormous support from the West, especially as they took on the Turkish military establishment,” says Bulent Aliriza, director of the Turkey Project at the Center for Strategic and International Studies in Washington. “This is now in doubt as they criticize Erdogan and he reacts strongly to their criticism.”

Erdogan appears to have been caught off guard by the sudden emergence of street-level opposition that emerged from a seemingly minor zoning dispute over a park in central Istanbul. Until now, he has almost always found a way to impose his will on Turkish politics. But after a long, dominant run in power, Erdogan’s pugnacious instincts have suddenly led him astray, with protesters provoking him into a conflict perhaps best handled by a mayor.