Probably the first newspaper in the country to endorse John Anderson for president was this town's famous progressive journal, the Madison Capital Times. Now the Cap Times is having second thoughts, and leaning toward Carter over Reagan. Elliot Maraniss, the editor, came away from an interview with Carter the other day and asked in a headline on the front page: "Why Not Reagan? It's a Question of Peace."

The State Journal, the bigger and more conservative paper in town, also endorsed Anderson. It too is having second thoughts -- but of a different kind. Robert H. Spiegel, the editor, wonders whether anything but an endorsement of Reagan wouldn't "favor" Carter. "I don't want that," he wrote in an internal memo.

So nobody has to check the polls or study the law of anticipated expectations. Anderson is on the wane -- even here in the heart of Anderson country. Accordingly, those of us who have been partial to the congressman from Illinois have some thinking to do.

Not that there is any reason to rue having felt sympathy for Anderson. He was, and remains, the candidate of thoughtful people. He is more experienced, more articulate and more informed than either Carter or Reagan. He has a far better grasp of the inner connections linking the major issues.

But the Anderson program has had its innings. The congressman has had strong play in the press and on television. He took part in a debate with Reagan. The country knows where he stands.

There remains no chance that he can win. There is almost no chance that he can carry a single state. The possibility he can open the way to the choice of another candidate by Congress or in the electoral college is even more remote.

So his role, willy-nilly, has become that of a spoiler. Depending on the area, a vote for Anderson is a vote for either Carter or Reagan, and those who have favored Anderson now need to ask which is worse -- and by how much.

Reagan has waged the less offensive campaign. He has moderated considerably many of the far-out things he and his backers said about welfare, the appointment of judges and Social Security. His economic advisers include men of strong, practical sense.

But he remains prone to woeful oversimplification. His capacity for work seems limited. The quality of his campaign staff does not bolster the claim that he would make superb appointments.

Above all, there is his insistence on withdrawing -- not reassessing or renegoiating -- but withdrawing the Strategic Arms Limitation Treaty from Senate consideration. Since that decision belongs to the Senate, the Reagan stance suggests plain ignorance. The strong implication is that, far from weighing the national interest in a judicious fashion on a controversial matter, he sees SALT as a vicious beast, a veritable monster that he must kill deader than dead, with a stake driven through its heart. That is a dreadful augury, which Reagan ought to repudiate.

President Carter has not given the country any reason to believe his second term would be better than his first. He seems to think, in the face of all the evidence, that he did well on energy and the economy. He promises to keep his White House advisers on the job. He has shown beneath the mean and petty exterior a mean and petty inner self.

Even his stance on the crucial issue of arms control seems dubious. The president promises he will push the SALT agreement to a vote in the Senate. He does not see that what held up SALT was his own feckless record in yielding to every radical pressure in the Persian Gulf, and Africa, and Asia and Central America. The surest way to kill SALT is for Carter to force a vote in the Senate while maintaining the foreign policy that has failed every test.

So far, I do not discern any weighty differences between Carter and Reagan. Before choosing one or the other, I want to see how the campaign develops in its final stages. I want to hear more from Reagan on SALT and more from Carter on the issue of competence. I know that the best is the enemy of the good. But I'm not going to abandon the test if there's nothing around that gives even dim promise of being good.