American conservatism is at one of its low ebbs. Conservatives seem divided, dejected, and drifting, caught between anger and indecision. The polls and pundits tell us that the political party we’ve made ours is headed for setbacks in the congressional elections, and further defeats loom ahead.

Of course, I’m talking about the state of American conservatism in 1958, when the Grand Old Party took a fall in that year’s midterm elections. That’s when Whittaker Chambers wrote a letter to his young friend, William F. Buckley Jr., at the still new conservative magazine, National Review.

If the Republican Party,Chambers warned, “cannot get some grip of the actual world we live in and from it generalize and actively promote a program that means something to masses of people — why, somebody else will.”

And the Republican Party, he continued, “will become like one of those dark little shops which apparently never sell anything. If, for any reason, you go in, you find, at the back, an old man, fingering for his own pleasure, some oddments of cloth (weave and design of 1850). Nobody wants to buy them, which is fine because the old man is not really interested in selling. He just likes to hold and to feel.”

Some of us can remember the intellectual atmosphere of the 1950s, when to be a conservative was considered less a persuasion than an eccentricity.

At the time, the Hiss-Chambers case had divided Americans into two hostile camps. Lionel Trilling, a professor of literature at Columbia and the author of “The Liberal Imagination,” scandalized his colleagues in the academic establishment when he described Whittaker Chambers as “a man of honor.”

It was Professor Trilling who, on scanning the political scene, announced that conservatives had no ideas — only “irritable mental gestures which seek to resemble ideas.”

The professor’s assessment of American conservatism was all too accurate at the time.

Conservative thought had lost its traction with the American people during the Great Depression and never regained it. The right was fast retreating into its dark little shop, where it would fall prey to the paranoia of politicians like Joe McCarthy and outfits like the John Birch Society.

Who with any political sense in the ‘50s would have predicted that, by the end of the century, conservatism would come to dominate American political thought?

How did it happen? It came to pass because American conservatism was able to articulate the country’s values in a way that made sense to a new generation of Americans.

A battle is always raging for the soul of American conservatism. It is a battle between those who would find a familiar place to hunker down, and those who would risk engagement with ideas and the world.

There have always been those who would reduce the conservative impulse to something narrow and mean and afraid — an exclusive little club restricted to Our Kind of People, rather than a great, open, embracing faith.

The great political achievement of Ronald Reagan was to transform a cozy club into a populist movement, and his example remains instructive. Much like Lincoln before him, The Great Communicator was willing to accept the know-nothings’ votes, but he drew the line at substituting their prejudices for his principles.

In Mr. Lincoln’s day, the Know-Nothings actually had a party, and its bogeyman was the Roman Catholic Church. Today’s demagogues use the latest wave of immigrants to much the same effect.

Today the party of Lincoln is being told it should demand that all illegal immigrants be deported, even if that means breaking up families, disrupting the economy and denying immigrant mothers medical care and their children an equal right to a college education.

Does anyone think these children will forget how their families, their mothers, and fathers, were treated once they grow up to become voters, as they surely will? Childhood hurts endure, and their fruit is bitterness.

Do we really want to let that kind of bitterness take root? Immigrant families once instilled an undying gratitude and reflexive patriotism in their children. I know. I was an immigrant’s child. Are we now going to plant resentment instead?

Cracking down on these newcomers and their children may be a good way to win the next election — and lose the next generation.

Tempting as it may be to demagogue the issue of illegal immigration, now is no time for conservatives to retreat to that dark little shop.