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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."

Another political strength, Erdogan's reputation as an able skipper of the Turkish economy, also appears damaged. The Turkish economy has grown by more than 40 percent during his 10 years in power and Erdogan has set ambitious economic goals for the next decade. But the Turkish lira has fallen significantly against other currencies since the protests, and prolonged unrest could further undermine confidence in the economy.

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.

After his harsh crackdown turned the situation into a global news story, Erdogan publicly derided demonstrators as terrorists and bums, briefly offered to meet with protest leaders, then turned to force again — projecting an image of erratic leadership. All the while, he lashed out against social media, while charging that the protesters were incited by foreign enemies and media, displaying an unsavory nationalism that has alienated former supporters.

But the damage may be reversible, largely because opposition parties are so weak. Moreover, Western leaders see Turkey as a crucial ally and need its help on key issues including Syria and Iran. They will likely be relieved if Turkey's turmoil subsides and they can go back to regarding Erdogan as a trusted partner.

Erdogan could also regain his standing with new mandate from the Turkish electorate.

Even without constitutional changes, Erdogan could still seek the presidency in the 2014 elections — although that would mean a diminished political role. Another option would be to abandon a pledge not to seek a fourth term as prime minister. An early general election could bolster Erdogan's position against a disorganized opposition, although his recent polarizing approach would likely translate into a smaller majority in parliament.

Ilter Turan, a professor of political science at Istanbul Bilgi University says that Erdogan could probably undo the damage if he took a more conciliatory approach, focused on the Turkish economy and got EU talks back on track.

But nearly three weeks into the demonstrations, he has shown little willingness to back down.

"His personality doesn't seem to allow for admitting mistakes and turning back," says Turan.

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Suzan Fraser in Ankara contributed to this report.

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