Jonathan Merritt, who writes On Faith & Culture for RNS, invited Peter Wehner — senior fellow at the Ethics and Public Policy Center and a contributing op-ed writer at The New York Times — to write this guest column on his blog.

(RNS) — We’re at a hinge moment in the public witness of American Christianity.

The evangelical Christian movement in America is being compromised and discredited by the way prominent leaders have associated themselves with, first, the Donald J. Trump campaign and now, the Trump presidency. If this is allowed to define evangelical attitudes toward political power, the public witness of Christianity will be undermined in durable ways.

I say this recognizing that the last election involved difficult choices upon which reasonable and well-intentioned people disagreed. I understand the argument of those who believed that Mr. Trump was the better of two bad options, whose policies would do less damage to the country than Hillary Clinton's.

But the worry is that now that the election is over and there is no binary Trump-Clinton choice, many evangelical Christians have lost the capacity to hold the president accountable when he transgresses norms, violates principles and acts in malicious ways. In fact, they have become among his most prominent and reliable public defenders.

Either by their public defense of Trump or their self-indicting silence, certain prominent evangelicals — including Franklin Graham, Eric Metaxas, Jerry Falwell Jr., Robert Jeffress, Ralph Reed and James Dobson — are effectively blessing a leader who has acted in ways that are fundamentally incompatible with a Christian ethic.

The same qualities that Mr. Trump showed during the campaign have continued in his presidency. He lies pathologically. Mr. Trump exhibits crude and cruel behavior, relishes humiliating those over whom he has power and dehumanizes his political opponents, women and the weak. He is indifferent to objective truth, trades in conspiracy theories and exploits the darker impulses of the public. His style of politics is characterized by stoking anger and grievances rather than demonstrating empathy and justice.

Evangelical Trump supporters aren’t responsible for the character flaws and ethical failures of the president. But by their refusal to confront those flaws and failures, they are complicit in the debasement of American culture and politics. Even more painful, they are presenting a warped and disfigured view of Christianity to the world.

A non-Christian I know recently told me that what is unfolding is “consistent with what sociobiology theorizes about religion: Its evolutionary purpose is to foster in-group solidarity. Principles serve rather than rule that mission.” This certainly isn’t my view of faith, but in the current circumstances – given what is playing out in public — this is not an unreasonable conclusion for him to draw. And he's not alone. This kind of perception is multiplying.

I’ve worked in politics much of my adult life, including in presidential campaigns and at the White House. I understand that governing involves complicated choices, transactional dealings and prudential judgments. No one ever gets things exactly right, and all who choose to serve deserve our prayers for wisdom. Politics is certainly not a place for the pursuit of utopia and moral perfection; rather, at its best, it is about achieving the best approximation of the public good, about protecting human dignity and advancing, even imperfectly, a more just social order. That is why Christians shouldn’t exile themselves from politics.

But with political involvement come temptations and traps, and it is the responsibility of Christians to act in ways that maintain the integrity of their public witness. And that is why this moment is so troubling. It seems clear to me, and I think to others, that many evangelicals, even unwittingly, are subordinating the Christian faith to partisan loyalties and political power.

“The church must be reminded that it is not the master or the servant of the state, but rather the conscience of the state,” Martin Luther King Jr. said. “It must be the guide and the critic of the state, and never its tool.” Today, far too many evangelical Christians are tools of the Trump presidency.

To be sure, the people with whom I have differences on this matter often do worthy work in other areas of their lives. But in this area, I believe their words and actions are harming the faith we share.

I’m speaking out at this time because I’m a Christian who places himself in the evangelical tradition and senses that some important lines have been crossed, some significant damage is being done, and some substantial repair work needs to take place. I hope others who share these concerns – who might feel anguished by what they perceive as the abuse of their faith – will take a stand in their own lives and in their own way. We can all be part of a politics of redemption.