Turkey’s prime minister, Recep Tayyip Erdogan, has declared war on “the man in Pennsylvania.”

This bizarre battle pits Erdogan against an elderly Turkish scholar of Islam named Fethullah Gulen, who lives in self-imposed exile in Saylorsburg, Pa., on a 26-acre compound called the Golden Generation Worship and Retreat Center.

The distance between Istanbul and the Poconos makes it hard to conceptualize this battle. Yet it will affect the future of democracy in a country viewed as a model of moderate political Islam.

Gulen hardly looks threatening. While sitting in his Saylorsburg study, he posts website sermons that promote a modern form of Islam, stressing education, free markets, democracy and religious tolerance. His followers in the Hizmet (Service) movement run a network of industries, media companies, colleges, charities and college-tutoring schools in Turkey, as well as a global network of 2,000 schools, including about 120 U.S. charter schools, that emphasize science.

His supporters see him as a modernizer and reformer (he got a green card as an exceptional educator). His foundations promote warm relations with other religions (he has apologized for anti-Semitic remarks made many years ago). And he is a strong proponent of Turkey becoming part of the European Union.

However, his detractors critique him and his movement as secretive and cultish, and claim he controls a shadowy network of supporters in the Turkish security services and bureaucracy that has a hidden agenda. That “opaqueness,” claims Alp Aslandogan, head of the Gulenist Alliance for Shared Values, is due to Turkish political culture, which long branded anyone who did not subscribe to secular “Kemalism” as an internal enemy.

Whatever its reasons, the non-transparency of the Hizmet network arouses suspicions, including an FBI investigation of some of its schools for possible money skimming, and the pending closure of another school in Philadelphia. And Hizmet’s secrecy makes it vulnerable to Erdogan’s attack.

Ironically, Erdogan and Gulen were allies for years in a joint effort to subordinate the coup-prone Turkish military to civilian control. This was a cause in which Gulen supporters in the police, judiciary, intelligence services, and press were extremely active. Neither Erdogan, whose party has roots in Islam, nor the Gulenists showed any concern for the non-transparency of show trials against generals, secular educators, and journalists. Known as Ergenekon and Sledgehammer, these trials were based on shaky evidence and doctored wiretaps and sent innocent people to jail.

But the two men have recently fallen out over democracy and corruption. Judged by his principles, Gulen seems the more democratic. When it comes to methods, however, the verdict is out.

Gulen angered Erdogan when he criticized the prime minister’s crackdown on environmental protesters last year, which sparked huge national demonstrations. The scholar rightly labeled the crackdown undemocratic. Score one for Gulen.

The two men finally parted ways over corruption. Erdogan blamed Gulen supporters inside the police and judiciary for bringing graft charges and leaking incriminating tapes against several cabinet ministers and against his own son, in the run-up to recent municipal elections.

Gulen was unrepentant. “If among those who conducted the graft investigations were some people who might be connected to the Hizmet movement, was I supposed to tell (them), ‘Turn a blind eye’? Did they expect me to do this?” he told the pro-Gulen newspaper Today’s Zaman.

The problem lies not in prosecution of corruption, however, but in the tactics — leaked tapes with heavy coverage by pro-Gulen media. Gulenists, of course, deny doing any leaking. As for Erdogan, he supported such tactics in the Ergenekon trials, but decries them when they hit home.

Why should Americans care about this dispute? Because Turkey matters. A rising economic power, it could become the first predominantly Muslim country to successfully meld Islamic values with pluralistic politics. And it belongs to NATO.

Yet Erdogan is using the fight with Gulen as an excuse to exert semi-authoritarian control over key areas of government. He has gutted large segments of the police and judiciary, removing or transferring thousands of supposed Gulen supporters, and is taking tighter personal control of the intelligence services.

With elections over, Erdogan has pledged that the Gulenists “will pay the price” for their supposed leaks. Erdogan’s party won a plurality by playing the victim, and blaming the Gulenists for slander; he is likely to continue this game.

Indeed, Erdogan is now using Gulen as an excuse to crush social media. After blaming a new leak from the foreign ministry on Hizmet, the prime minister blocked YouTube and banned Twitter but the country’s highest court reversed the ban Thursday. He is trying to censor the Internet.

And the Turkish leader has asked President Obama to take action against Gulen, saying, “The person who is responsible for the unrest in Turkey lives ... in Pennsylvania. You have to take the necessary stance.” The White House denied Erdogan’s claim that Obama reacted “positively” to his request for action on Gulen.

Sadly, this battle is not about modernizing Islam or about building better democratic institutions. Instead, it pits an elected leader with an authoritarian bent against an Islamic scholar with appealing ideas but secretive, suspect methods.

I’d like to ask “the man from Pennsylvania” about his intentions, but so far, have not been granted one of his rare interviews. As Erdogan goes on the offensive, Gulen should lift the veil of secrecy from his organization. Transparency may be his best defense.

Trudy Rubin is a columnist and editorial-board member for the Philadelphia Inquirer.