Who is the most important European alive today? I nominate the Dutch politician Geert Wilders. I do so because he is best placed to deal with the Islamic challenge facing the continent. He has the potential to emerge as a world-historical figure.

That Islamic challenge consists of two components: on the one hand, an indigenous population’s withering Christian faith, inadequate birthrate, and cultural diffidence, and on the other an influx of devout, prolific, and culturally assertive Muslim immigrants. This fast-moving situation raises profound questions about Europe: will it retain its historic civilization or become a majority-Muslim continent living under Islamic law (the Shari’a)?

Geert Wilders, surrounded as always by bodyguards.

Wilders, 46, founder and head of the Party for Freedom (PVV), is the unrivaled leader of those Europeans who wish to retain their historic identity. That’s because he and the PVV differ from most of Europe’s other nationalist, anti-immigrant parties. 

The PVV is libertarian and mainstream conservative, without roots in neo-Fascism, nativism, conspiricism, antisemitism, or other forms of extremism. (Wilders publicly emulates Ronald Reagan.) Indicative of this moderation is Wilders’ long-standing affection for Israel that includes two years’ residence in the Jewish state, dozens of visits, and his advocating the transfer of the Dutch embassy to Jerusalem.

In addition, Wilders is a charismatic, savvy, principled, and outspoken leader who has rapidly become the most dynamic political force in the Netherlands. While he opines on the full range of topics, Islam and Muslims constitute his signature issue. Overcoming the tendency of Dutch politicians to play it safe, he calls Muhammad a devil and demands that Muslims “tear out half of the Koran if they wish to stay in the Netherlands.” More broadly, he sees Islam itself as the problem, not just a virulent version of it called Islamism.

Finally, the PVV benefits from the fact that, uniquely in Europe, the Dutch are receptive to a non-nativist rejection of Shari’a. This first became apparent a decade ago, when Pim Fortuyn, a left-leaning former communist homosexual professor began arguing that his values and lifestyle were irrevocably threatened by the Shari’a. Fortuyn anticipated Wilders in founding his own political party and calling for a halt to Muslim immigration to the Netherlands. Following Fortuyn’s 2002 assassination by a leftist, Wilders effectively inherited his mantle and his constituency.

The PVV has done well electorally, winning 6 percent of the seats in the November 2006 national parliamentary elections and 16 percent of Dutch seats in the June 2009 European Union elections. Polls now generally show the PVV winning a plurality of votes and becoming the country’s largest party. Were Wilders to become prime minister, he could take on a leadership role for all Europe.

But he faces daunting challenges.

Sitting shoulder to shoulder, Daniel Pipes and Geert Wilders in 2006.

The Netherlands’ fractured political scene means the PVV must either find willing partners to form a governing coalition (a difficult task, given how leftists and Muslims have demonized Wilders as a “right-wing extremist“) or win a majority of the seats in parliament (a distant prospect). 

Wilders must also overcome his opponents’ dirty tactics. Most notably, they have finally, after 2½ years of preliminary skirmishes, succeeded in dragging him to court on charges of hate speech and incitement to hatred. The public prosecutor’s case against Wilders opens in Amsterdam on January 20; if convicted, Wilders faces a fine of up to US$14,000 or as many as 16 months in jail.

Remember, he is his country’s leading politician. Plus, due to threats against his life, he always travels with bodyguards and incessantly changes safe houses. Who exactly, one wonders, is the victim of incitement?

Although I disagree with Wilders about Islam (I respect the religion but fight Islamists with all I have), we stand shoulder-to-shoulder against the lawsuit. I reject the criminalization of political differences, particularly attempts to thwart a grassroots political movement via the courts. Accordingly, the Middle East Forum’s Legal Project has worked on Wilders’ behalf, raising substantial funds for his defense and helping in other ways. We do so convinced of the paramount importance to talk freely in public during time of war about the nature of the enemy.

Ironically, were Wilders fined or jailed, it would probably enhance his chances to become prime minister. But principle outweighs political tactics here. He represents all Westerners who cherish their civilization. The outcome of his trial and his freedom to speak has implications for us all.

Mr. Pipes is director of the Middle East Forum and Taube distinguished visiting fellow at the Hoover Institution of Stanford University.