The prevailing mentality among Beltway Republicans is that passage of an imperfect immigration bill before the November elections is better than no bill at all. They might just find out how wrong they are when they experience the inevitable conservative backlash.

Why do we have to be faced with these false choices? The enactment of an imperfect bill, even if it would help to preserve the Republican majority in November, would be a classic case of sacrificing the long-term good for short-term political benefit.

I strongly believe we need to preserve a Republican majority, even though that majority is often controlled by dictatorial moderates — as in the Gang of 14, seven of which are Republicans. The election of a true Democratic majority would have potentially horrifying consequences on domestic and national security issues across the board.

But with the immigration, we’re not talking about some little throwaway issue, but one whose resolution could determine whether this country will ultimately retain its national identity. If anything closely resembling the Senate bill becomes law, we will be stacking the decks against ourselves in what already promises to be a formidable struggle to preserve the unique American culture.

The idea that we can later tweak an imperfect bill is pernicious folly. Not only is this bill far from merely “imperfect,” the reality is that the law of entropy usually applies in politics as well as thermodynamics. If anything, an imperfect bill will, over time, become more imperfect.

Remember the Campaign Finance Reform Bill that President Bush signed, after having campaigned against it, offering the half-hearted assurance that the Supreme Court would probably declare it unconstitutional anyway? Well, they haven’t, have they?

What’s more, while the bill put a selective dagger through free speech in the critical 60 days prior to the election, it still didn’t fulfill its specious promise of taking big money out of politics.

So now, Sen. McCain and his band of merry “reformers” want to further massage the bill and carve the imperfections of out it. Every version, including the present one, is presented as the bill to end all bills. But additional iterations just make matters worse, without correcting any of the so-called imperfections.

The last thing we need is another imperfect bill, this one on immigration, even if it means that Republicans have to take a hit in November.

As much as I prefer imperfect Republicans over Democrats and fear the consequences of a Democratic majority, this is one issue where we simply have to draw the line. This bill, which could easily result in an exponential wave of immigrants entering this country over the next two decades alone, whom our P.C. culture will not even encourage to assimilate, must be vigorously opposed.

While I agree that we can’t allow the perfect to be the enemy of the good, we simply can’t risk bargaining away the very identity of this nation on the illusory promise that holes in the bill will be patched over in time. If there isn’t enough time to craft a nation-preserving bill before the election, there won’t be afterwards either.

Having said these things, I don’t accept the premise that failure to pass a deeply flawed bill is politically suicidal for Republicans. If you believe that, you probably believe the conventional wisdom that elections are controlled by the mushy middle.

To the contrary, the Republicans who have been most successful in national elections are those who have held firm on conservative principles. Unlike the base of the Democratic Party, the Republican base is not fringe or extreme, but mainstream conservative. Those who want to preserve the unique American culture and the English language are not extremists, nativists or racists, which shouldn’t even have to be said.

Ronald Reagan won landslide elections through unabashed conservatism. And, the decline in President Bush’s approval rating is not just due to “all bad news all of the time” on Iraq, but that he is perceived to have abandoned his conservative base on far too many issues.

Much of the reason the Republican Senate is so disappointing to conservatives is that the moderate and liberal tail is wagging the conservative dog. The McCain moderates are hamstringing conservatives — and even some of the conservatives have lost their nerve.

I don’t remember a time when Beltway politicians, including way too many Republicans, have been so tone deaf on an issue and so complicit on a matter that could severely damage the long-term interests of this nation.

Let principled conservatives try on their obstructionist hats for a change. In this case, for now, passing no bill is better than passing the Senate bill. They should have the courage to take their case to the voters in November.