I am a Zionist because I am an atheist and a Jew. Zionism has allowed someone like me to preserve my faith in the sovereignty of human beings over their fate, while maintaining a deep and continuous commitment to the Jewish people and its future.
The dawn of enlightenment, emancipation and the advent of modernism presented Jews with unprecedented challenges—how to remain Jewish and how to preserve the Jewish people in the absence of belief in God, and performance of religious duties.
While those who continued to believe in God could choose between various streams that reformed Jewish life, the Jews who embraced the modern idea that it is not god that created man and woman, but rather man and woman who created god, could choose either to assimilate into their host nations, fight for a Communist utopia, or become Zionist.
Zionism won. Communism failed to deliver salvation and Tikkun Olam, or to preserve Jewish life. Assimilation succeeded for some individuals but obviously failed in preserving Jewish life. Of all the answers given to the challenges of modernization, only Zionism, by reformulating Judaism as a culture and civilization grounded in the ancient land and history of the Jews, allowed individuals to remain true to the ideas of the enlightenment while contributing to a thriving Jewish life. Zionism has succeeded so much so that even religious and ultra-Orthodox Jews, who might not have needed national expression, have adopted and adapted Zionism into their religious identity.
Zionism won beyond Israel too. Even for those not living in Israel, Zionism is a powerful means of expressing Jewish identity. For many Jews, theists and atheists, engagement with Israel and Zionism, even without living there, is a fulfilling way of being Jewish. Israel and zionism are so powerful, that just a short visit to israel (like Birthright) can have an effect on Jewish identification greater than years of Jewish education. Whether it is by advocating for Israel on campuses or the Hill, or whether it is (sadly) by engaging in anti-Israel activity, relating to Israel is how many Jews are Jewish. Both in Israel and the diaspora, Zionism is the most powerful force sustaining secular Judaism.