It’s terrible to politicize a tragedy.

But it has to be done, urgently, in the wake of the Dallas police massacre that left five officers dead and seven wounded, including one civilian.

America is in a fragile state — a volatile state. Not since the summer of 1968 have we seen racial tensions so high and political divisions so deep. There is plenty of blame to go around. I could make a list a half-mile long. So could you.

But blame is poison. It exacerbates and perpetuates divisions; it never heals them. If there’s one thing that could truly break America apart, it’s blame. To advance as a nation, we have to look forward, as we’ve always done, not backward.

In about a week, Republican Party leaders will head to Cleveland to nominate a presidential candidate. Before that convention convenes, those leaders need to come to grips with an obvious and inalterable fact: Donald Trump is temperamentally unsuited to be president of the United States.

America needs a steady hand in the White House, especially now. Trump’s is anything but. He’s a blamer-in-chief, a spurting drum of gasoline in incendiary times, and the Party of Lincoln is about to put him up for president. It’s totally irresponsible. (Trump has been cautious in his words about Dallas so far, but how long will that last?)

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And here’s the more appalling thing: the Republicans know it. Republican National Committee chairman Reince Priebus knows it; members of the House and Senate know it; most delegates know it. But they’re planning to nominate Trump anyway because they’re too afraid to amend convention rules and alienate die-hard Trump supporters. They’re too afraid to stand up, be counted and let the chips of history fall where they may.

These are today’s Republican leaders (with a handful of exceptions). These are the supposed progeny of Abraham Lincoln, Teddy Roosevelt and Ronald Reagan. They privately grouse about Trump’s recklessness, and do nothing. They are cowards.

Roosevelt would have loved gutsy Kendal Unruh. Unruh is an RNC rules committee delegate from Colorado and a leader in the anti-Trump movement. She and a group of clear-eyed confederates are this generation’s true Republican leaders — Roosevelt’s “Men (and Women) in the Arena,” if you will. They’re working ‘round the clock, under incredible scorn and threats from the likes of former GOP vice presidential candidate Sarah Palin and others, to force a rules committee vote that would free Republican delegates in Cleveland to vote their consciences on the first ballot. If they succeed — and they’re close — they may very well prevent the Republican Party from committing moral and political suicide.

I spoke with Unruh by phone on Thursday. She was driving, and I could hear in an instant how busy she is, how transfixed in her task. A few hours later, as the images from Dallas reached our TV screens, that task became all the more imperative. The GOP cannot nominate such a fundamentally flawed man for president.

A lot of Republicans are saying you’re either for Donald Trump or for Hillary Clinton. Nonsense. Neither has been formally nominated yet. Until such an unholy nomination is consecrated in Cleveland, there’s a fight to be had, for the future of the Republican Party and the future of America.

Last chance to get in the arena, folks.

William F. B. O’Reilly is a consultant for Republicans.