The Panama Canal treaties, heaven help the Republic! In the Senate chamber with its glossy pseudo-elegence, owing something perhaps to MGM, Sen. Harry F. Byrd Jr. (I-Va.) is droning on with all the vibrancy and dynamism of a sleepy night watchman in a marsh-mallow factory. He is repeating the warmed-over testimony of retired admirals and generals opposed to the treaties.

Tactics of obstruction and delay are dragging out the process of ratification until it has become an intolerable charade. The 15 or so undecideds have no real reason to perch on the fence, since all the arguments pro and con have been rehearsed a dozen times.

It was a welcome relief when with remarkable forthrightness and courage a senator who had every reason to duck and waver stood up and declared for the treaties. Thomas J. McIntyre (D-N.H.), whose term expires this year, is marked for extermination by the radical right led by Gov. Meldrim Thomson and his partner William Loeb, publisher of the Manchester Union-Leader.

"By proceeding from the flawed premise that all of us are alike," McIntyre said, "it is easy for ideologues to conclude that we must see every issue as they see it - unless there is something sinister in our motivation. And they proceed from that premise with an arrogance born of the conviction that they and they alone have a corner on patriotism, morality and God's own truths, that their values and standards and viewpoints are so unassailable they justify any means, however coarse and brutish, of imposing them on others."

McIntyre had hardly finished speaking when Loeb opened up with a front-page editorial, a favorite device, attacking him and quoting him as having made a disparaging remark about the voters in his home town of Laconia. A wire-service story in the same edition belied the quote in the Loeb editorial.

Elected to a short term and then twice reelected to full terms, McIntyre as a member of the Senate Armed Services Committee has won a reputation for a sane and reasonable approach to defense and security. Under normal circumstances he would have little trouble this fall. But Thompson and Loeb, working with the state Conservative Caucus, are getting a firmer grip on the state.

Thompson has hinted he might run against McIntyre for the Senate seat. He is busy building himself up around the country as a leader of the radical right. In Los Angeles he made an inflammatory speech to a convention of the John Birch Society attacking President Carter for leading "America along the path of communism to national suicide."

If he runs for the Senate, he will give up what is likely to be sure reelection to a fourth two-year term as governor. Looking forward to 1980, Thompson puts a high premium on the governorship since, again, New Hampshire will be the first state with a presidential primary. That will be Thomson's opening to start the bail rolling for a conservative candidate.

That would presumably by Ronald Reagan, the former governor of California, although Loeb, whom McIntyre has called "the master practitioner of the politics of threat and vengeance," has some doubts about Reagan's conservatism. The Thomson-Loeb partnership has been busy drumming possible Republican candidates out of consideration.

Foremost, of course, is Sen. Howard Baker of Tennessee, a leader of the pro-treaty forces. John Connally of Texas has been roundly denounced as a dangerous one-worlder. The only acceptable Republican is Sen. Robert Dole of Kansas. In the long winter in tax-free New Hampshire, they dream of tickets for 1980 - Reagan and Dole or Reagan and Thomson or - but this is pretty far out - Thomson and Dole.

Even in his own fiefdom. Thomson is now and then rebuked. Accepting an invitation to visit South Africa, he called the State Department "un-American" and John Vorster "one of the great world statesmen of today." Fourteen of New Hampshire's religious leaders issued a statement saying that "our Christian consciences will not allow the [governor's] statment to go unanswered." And naturally Loeb rushed to Thomson's defense calling the clergymen innocents who had been brain-washed and praising the regime in South Africa "for doing their best to bring these blacks out of the jungle."

McIntyre's decision in favor of the treaties was obviously not an impulsive act. He had spent many weeks in careful study of the treaties themselves and the pros and cons put forward at the start of the controversy.

His decision should be an example to waverers who face odds much safer than those that confront the senator from New Hampshire. The potential Republican opposition thus far is not too impressive. Leaving aside the weight in the political scales, McIntyre has stood up against the computerized New Right, and for that alone he deserves high marks.