Vivisections are a nasty business.

Think Mel Gibson in the final scene of the film, “Braveheart.”

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Actually, don’t.

Consider instead the disembowelment of the Republican Party happening right before our eyes. It’s less gruesome, but only slightly less so.

The GOP is splayed out on the altar of American politics, and we’re all getting a good look at its innards. It isn’t pretty.

What we’re seeing is less orderly that many of us imagined. The three legged stool of American conservatism we so often talk about — less government and taxes, traditional social values and a strong national defense — is not alone in there. Wedged into the crevices, between the spleen and kidney, is a nasty nativist tumor. The small government organ is punctured and bleeding, and the isolationist appendix that doctors swore was removed in 1941 isn’t only still there, it’s beginning to function again.

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Most concerning, though, is the scarring we see in the brain’s limbic area, the system that controls anger. It’s preventing the thing from turning off. The result is a stark raving mad party at cross purposes with itself. That’s not very attractive.

Battlefield surgery isn’t going to fix the GOP. It needs to spend the next several years deciding what it is. Try selling a product to an already skeptical consumer that you can’t easily explain. It’s near impossible. (Yelling the sales pitch isn’t much help either.)

I’m no doctor. But I’m going to offer a prescription for a new and improved Republican Party anyway. My foundation for a new Republican Party is this: One America. One set of rules.

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One American means no special rights for anyone. It means no affirmative action and it means no corporate tax breaks. It means one set of laws for everyone — a single tax rate, no industry subsidies (sorry, Iowa corn growers), everything in English (in the public sector), and equal funding for every school child. (If generous Americans want to buttress learning in poorer school districts, they should be encouraged to do it through not-for-profits that don’t get government money.) It means legal immigration with no exceptions.

At the same time, the Republican Party would have to take action when any of our nation’s citizens are being treated unfairly. If African-American kids are being punished more severely for infractions than other American kids, it would be the stated duty of the Republican Party to step in. If Hispanic youngsters are being shuffled through school without having attained proper English skills, it would up to the Republican Party to make a stink about it. If equally qualified women are making less money than equally qualified men in a government job, the Republican Party should be on it.

Americans are revolting against their government because they think it’s unfair. They’re right. Washington and state governments are constantly changing the rules for the well connected and for the loudest special interest groups. It’s made our tax code a joke and our regulatory system more complex than DNA.

Equal treatment under the law: That was the whole idea of Abraham Lincoln’s Republican Party. It was why it went to war to end slavery.

Who would have guessed that a century and half after Lincoln’s Emancipation Proclamation, we’d have tens of thousands of different sets of rules for tens of thousands of different interests and demographics.

The Democratic Party tries to socially engineer equality with tax dollars in the name of “social justice.” It hasn’t worked. It’s nearly bankrupted us and it’s turned many Americans against one another.

The Republican Party should offer a sharp and easily understandable alternative. It should insist on one set of rules and let individual Americans succeed or fail under them.

If the GOP is to survive, it needs to a clear mission statement. One America. No matter what or who you are.

That’s where I’d go. People will get that.

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