ARI SHAPIRO, HOST:

Once again, voters in Turkey will try to elect a president on Sunday. It's a runoff between the top two candidates after the first round of elections did not produce a clear winner. Turkey's strongman incumbent Recep Tayyip Erdogan has been in power for two decades, and he faces his biggest challenge ever in opponent Kemal Kilicdaroglu. That makes it a critical election for a regional powerhouse and a key U.S. ally. NPR's Fatma Tanis is covering it from Istanbul. Hi there.

FATMA TANIS, BYLINE: Hi.

SHAPIRO: What's the scene like there right now?

TANIS: Well, it's vibrating with anticipation. You hear political debates on the street. I passed by one young man who was passionately trying to convince his neighbor to switch sides, to no avail, it seemed. Later, outside the spice bazaar today, there were rivaling campaign buses next to each other, blasting their own music, and crowds of supporters were dancing each to their own political tune. You know, elections are a big deal in Turkey, and voter turnout is really high. We're talking about 89% turnout in the last round. People here feel that their lives are directly impacted by politics. And for many, this election in particular is a matter of life and death, they say.

SHAPIRO: Personally, the stakes are huge for individuals, but geopolitically, the stakes are also huge. This has been called the most consequential election for Turkey's century-old democracy. Explain why.

TANIS: Well, many here see it as a referendum vote between two different Turkeys. We already know what Erdogan's Turkey looks like after two decades in power. He changed the parliamentary system to a presidential one five years ago. He gave himself sweeping powers. He's known for his religious nationalist rhetoric. But critics say that his one-man rule is just not working. Turkey's economy is in shambles. Erdogan's government struggled to respond to a devastating earthquake in February. And then there are serious concerns about the future of civic freedoms. If Erdogan wins, what would be his third term? His opponent, Kemal Kilicdaroglu, on the other hand, has promised to change Turkey's governing system back to the parliamentary one, has also promised to end corruption, protect democratic rights. But his own party has a lot of historic baggage with many voters, and Kilicdaroglu has struggled with presenting himself as an alternative to Erdogan, who's seen as a much more charismatic leader.

SHAPIRO: The vote was so close two weeks ago. What's happened in the last two weeks, and is it likely to make any difference?

TANIS: Well, so there's a pocket of voters who aren't happy with neither Erdogan nor his opponent. They cast their votes mainly in protest for a third candidate in the first round. Now, that candidate has announced he's backing Erdogan, but that doesn't mean those votes will travel with him. So that's one thing to watch. Another thing is the opposition is struggling a little bit with morale after their loss in the first round, which obviously works to Erdogan's advantage. I met a 28-year-old man today working at a toy shop. His name is Yunus Emre. He voted two weeks ago but now feels dejected and is not sure if he'll show up this Sunday.

YUNUS EMRE: (Speaking Turkish).

TANIS: He says despite all of the many issues under Erdogan, if he's still able to maintain his popularity, then there's something seriously wrong with the opposition, or there's simply no hope for change at all. He says he knows many people around his age that feel the same. And analysts say those votes are critical in deciding the fate of this country.

SHAPIRO: Turkey is such a key U.S. ally. What could be at stake for American interests in this election?

TANIS: Well, one big thing is President Erdogan's personal relationship with Russian President Vladimir Putin. The two have gotten closer over the past years, and that's translated into policy. Turkey has not joined in Western sanctions against Russia. It has also delayed the ratification of Sweden's membership into NATO. And so that is one big question Western allies are watching - how the election will shape up.

SHAPIRO: That's NPR's Fatma Tanis in Istanbul. Thanks for your coverage.

TANIS: Thank you. Transcript provided by NPR, Copyright NPR.