One e-mailer responded in a way that I think exemplifies the view of too many evangelicals. He advised me not to "minimize" the doctrinal differences between Catholics and evangelicals. And he accused me of "blurring" the lines between evangelicals and Catholics and of advocating for a "one-world religion."

Thankfully, most evangelicals wouldn't be that uncharitable toward our Catholic brothers and sisters. But, sadly, a minority would endorse that characterization. They need to realize that they, too, have a stake in who is elected pope, because without a strong pope, evangelicals will lose their best allies in the most important cultural and political battles of our age.

Catholics and evangelicals (and to a lesser extent orthodox Jews and Mormons) have formed a formidable partnership in recent decades against the threats of secularism, relativism and Islamism.

Doctrinal differences remain, of course, but the Catholic-evangelical alliance has reshaped American politics. In many cases, Catholics have provided the intellectual framework and vocabulary to discuss Christianity's vital role in our democracy, while Protestants have contributed fervor and youth.

We do not agree on every issue. But on the essential ones -- those both faiths consider "non-negotiables" -- Catholics and evangelicals are allied.

We both champion the idea -- the truth -- that there are reliable standards of right and wrong to which all institutions, including government, must adhere. We stand together in proclaiming that all human life has equal dignity and worth. And we stand together in defending the traditional and time-honored conception of marriage as a union of one man and one woman.

Last year millions of evangelicals and Catholics came together to support Rick Santorum during the Republican presidential primaries and then Mitt Romney in the general election. And we continue to stand together in opposition to the Obamacare contraceptive and abortion mandate.

No one can doubt that the evangelical-Catholic alliance will continue to be necessary, as both churches attempt to fend off the federal government's increasing attempts to conscript churches into advancing its objectives against their consciences.

Beyond politics, the West is suffering from what can be called a crisis of brokenness -- broken institutions, broken families and broken souls. In a society in which there seem to be fewer citizens who understand where our liberty comes from (God), strong churches -- evangelical and Catholic -- are essential.

As an evangelical, I was delighted that the last two popes were moral and theological giants. Together, John Paul II and Benedict XVI gained many evangelical admirers by preaching against the "culture of death" and the "dictatorship of relativism" and for a "culture of life."

And, as Catholic theologian George Weigel argues in his new book Evangelical Catholicism, John Paul II and Benedict XVI introduced a new "evangelical" period for the Catholic Church -- an era in which the Catholic Church offered a confident rebuttal to the false promises of the secular world.

I don't mean to downplay the real and significant theological differences between our two faiths. But Catholics and evangelicals need to remain allied, and in solidarity, against the increasingly aggressive secularism of our age.

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Former presidential candidate Gary Bauer is president of American Values and chairman of the Campaign for Working Families