THE SPLIT in the Senate and his leadership of the Republican swing bloc have given Sen. Howard H. Baker Jr. (R-Tenn.) virtual life-or-death power over the new Panama Canal treaties - and this at a time when Mr. Baker, eyeing his party's 1980 presidential nomination, is eager at once to establish a responsible "national" image, which means pro-treaty, without alienating anti-treaty Republican conservatives. He could have stayed in his shadows. Instead, he chose to walk the high wire, traveling to Panama and there conducting a remarkable intervention meant to bring together the Panamanian nd Senate treaty positions and not incidentally, to show Howard Bakery as the fellow who pulled it off.

The bottom line is whether the United States and Panama can come aboard to have helped, he deserves the points. The essence of what he is asking seems to be to somehow subject to the ratification process the executive-written language of the Oct. 14 Cater-Torrijos communique. In that document, Gen. Omar Torrijos clarified the United States' post-year-2000 claim to intervene militarily and to have its ships accorded priority emergency passage. If Panama could stomach the communique's instrusion upon its sovereignty, it can perhaps take the Baker additions too.

But let Mr. Baker's fancy footwork not be confused with statesmanship. He is gesturing to American primitives and tightening the screws on Panama in a manner all too suggestive of Teddy Roosevelt's high-handedness in grabbing the Zone in the first place. It is not the senators finesse but Gen. Torrijos's desperate need for the treaties that makes this gambit possible. Moreover, it is silly to think that anyone can anticipate in such detail the particular contingencies, justifying the new language, that will arise in the next century. We should thought better of Mr. Baker if he simply stated that, yes, certain gestures might be necessary, as a practical political matter, for purpose of ratification, but that the American public should have no illusions about what it will require to keep the canal open and operating. It can't be done by military force - as the senator must know. We would like to have heard him acknowledge will readily concede: that continued American use depends on keeping the goodwill of the Panamanians, not on imposing concessions bound to rankle nationalist Panamanians in the years ahead.