The resounding victory by opposition candidate Ekrem Imamoglu in last week’s mayoral election in Istanbul delivered a sharp blow to Turkish President Recep Tayyip Erdogan and his ruling Justice and Development Party, or AKP, whose 17-year grip on power suddenly looks a little less tight. In addition to a resurgent opposition, Erdogan now also faces rumbles of discontent from within the AKP and a looming challenge from several of his own former allies who are planning to launch a new center-right party. But both the opposition and Erdogan’s erstwhile AKP partners face an uphill task taking on the man who has dominated Turkish politics for so long.

Imamoglu’s convincing victory—he won by 800,000 votes, 9 percentage points ahead of the AKP’s candidate, Binali Yildirim—was well deserved, doubly so since the poll was a dubious rerun, forced by a grudgeful AKP that refused to accept Imamoglu’s narrow, original win back in March. Erdogan and his party, citing “irregularities,” pushed election authorities to nullify those results and run the ballot again.

The opposition Republican People’s Party, or CHP—previously lambasted for weak leadership, disorganization and vicious infighting—finally hit on a winning formula. Imamoglu, little known outside of the Istanbul suburb where he served as mayor for four years and where he proved his mettle as an administrator, was both politically clean and charismatic. His ability to work a crowd with a message of hope struck a chord with an electorate hurt by Turkey’s faltering economy and hungry for change. It was even reminiscent of Erdogan himself at his peak—in sharp contrast to the AKP’s own candidate, a former prime minister handpicked to run by Erdogan, no less. For all of Imamoglu’s electoral skills, Yildirim’s diffident performance, coupled with a lackluster and often ham-fisted campaign, cost the AKP the election.

The AKP’s attempt to push bogus allegations that Imamoglu was secretly in league with Greece smacked of desperation. But then it outdid itself, with the engineered “leaking” of a letter from Abdullah Ocalan, the jailed Kurdish leader of the militant Kurdistan Workers’ Party, or PKK—considered a terrorist group by the U.S. and the EU, as well as Turkey—advising supporters of Turkey’s pro-Kurdish Peoples’ Democracy Party, or HDP, to remain “neutral” in the election. Instead, the HDP urged its supporters to vote for Imamoglu. Meanwhile, supporters of the AKP’s parliamentary allies—Turkey’s fiercely anti-Kurdish, far-right National Action Party, or MHP—reportedly stayed home.

Yet the CHP now faces a struggle both in administering Istanbul and in using its historic victory as a stepping stone to success in national elections. Imamoglu’s pre-election promise to investigate the cause of the municipality’s reported $3.7 billion debt—and the $145 million allegedly transferred to foundations close to Erdogan’s family—may not be easy to deliver, given the influence the central government still has over the municipality. By law, municipalities in Turkey receive 6 percent of tax revenues from their metropolitan area, of which only 60 percent is allocated directly. The central government also retains final approval over budgets for major municipal projects, leaving plenty of scope for Ankara to restrict funds, forcing potentially unpopular cuts in public services.

The new mayor of Turkey’s largest city and economic hub also stands to lose control of the municipality’s vast web of companies responsible for everything from water and gas supplies to public transportation and bakeries. Ankara has already announced plans to transfer the authority over those entities from city mayors to elected council chambers, in which the AKP mostly holds a majority of seats, including Istanbul. The municipality is Istanbul’s biggest employer, so such a loss in control over it would also make it difficult for Imamoglu to deliver on his promise to get tough on city employees who use their positions as patronage platforms and vehicle for party politics.

It won’t be any easier nationally for the CHP to maintain its momentum for Turkey’s next scheduled parliamentary elections, which aren’t until 2022, and presidential and local elections in 2023. Not surprisingly, Imamoglu is being mentioned as the CHP’s likely next presidential candidate. One opinion poll already shows him with 60 percent name recognition outside of Istanbul—no mean feat given that virtually all of Turkey’s mainstream media openly support the AKP, granting Erdogan and his party blanket, uncritical coverage.

The CHP now faces a struggle both in administering Istanbul and in using its historic victory as a stepping stone to success in national elections.

But name recognition doesn’t automatically translate into votes, and it’s questionable to what extent the CHP can expand from its urban and coastal support bases to appeal to Turkey’s conservative, rural hinterland—where the AKP is strongest—and the predominantly Kurdish southeast. The CHP’s existing alliance with the right-wing Good Party has helped broaden its appeal, but given the CHP’s regional base, the best it can hope for is to be the major player in a more broadly based coalition.

Much, however, will still depend on whether an anticipated split in the AKP actually happens. Two AKP heavyweights—former President Abdullah Gul and former Economy Minister Ali Babacan—are expected to found a new party that could tap into the same disquiet over Turkey’s economic malaise and widespread yearning for change that underpinned the CHP’s success in Istanbul. If so, they could split the center-right religious vote and make a CHP-led coalition more likely in 2022.

While there are no signs yet that the AKP may be about to abandon Turkey’s most powerful president since Mustafa Kemal Ataturk, there are signs of growing divisions in the ranks. It was revealing that Erdogan failed to publicly thank Yildirim—himself no political lightweight—for his efforts in the Istanbul race. The AKP’s parliamentary group reportedly wants to trim some of the wide-ranging executive powers Erdogan assumed following last year’s transition to a presidential system, returning them to the Turkish parliament, and to end the ban on MPs serving as government ministers. The long lead time until the next elections means Erdogan has no need to make hasty changes and can wait for the economy to pick up, in the hope it will be enough to boost support for him and the AKP.

For now, he appears content to polish his image on the international stage. Photo ops with world leaders at last week’s G-20 summit in Osaka were given blanket coverage in Turkey’s supine media, as was a one-on-one meeting with U.S. President Donald Trump, which led to an apparent easing of tensions over Turkey’s plans to purchase Russia’s S-400 missile defense system. But while that news caused both the floundering Turkish lira and the Istanbul stock market to rally, Erdogan has reiterated plans to receive the first S-400s this month, raising the question of what, if anything, he and Trump actually agreed to.

A major confrontation with the U.S. over the issue is still a possibility, as is a separate face-off with the European Union over Turkey’s plans to send a second drill ship to search for natural gas in the Mediterranean within the exclusive economic zone claimed by Cyprus. The ship in question, the Yavuz, is currently anchored off Turkey’s southern coast, perhaps waiting for a signal from Ankara. Any escalation over Cyprus or the S-400s will inevitably hit the lira, with serious impacts on the weak Turkish economy, which economists have been warning is in for another rough patch after the summer’s uptick of tourism income and the seasonal benefit of low food prices.

But another economic crisis would, however, give Erdogan the chance to trot out his standard excuse used so many times over the past decade: blaming problems on nefarious Western intervention, as opposed to his own saber-rattling and poor policy choices, which until this year has been enough to maintain his and his party’s support. The question now, after Imamoglu’s victory in Istanbul, is whether the Turkish electorate will continue to buy it.