THE NUCLEAR FREEZE is now a runaway horse, and the Rough Rider in the White House inadvertently applied the whip as he tried to drive it back to the stables.

The morning after the president said at his White House press conference that a freeze would be "disadvantageous -- even dangerous," the two Senate sponsors, Edward M. Kennedy and Mark O. Hatfield, held a press conference of their own and thanked the president from the bottom of their hearts for what he had done for their cause.

What he had done, of course, was to draw the line between their proposal and the so- called "freeze" of Sens. Henry Jackson and John Warner. By endorsing Jackson-Warner, in the context of saying that the Soviets could "absorb" a nuclear strike by us and retaliate, the president made it perfectly clear that Jackson-Warner is strictly his kind of nuclear policy: reduce arms by making more.

"Voodoo arms control," Kennedy called it happily.

Kennedy and Hatfield are confident that Reagan's effort to throw the discussion back into the arcane numbers game, which the public cannot play, will fail.

The country has somehow slipped out of the technological corral. They want simplicities. They are marching under the banner of "Enough is Enough." The organizers of the nuclear freeze campaign cannot keep up with it. They are opening a Washington office soon. Despite all efforts by Reagan and his men to coax the country into regarding nuclear war as, in White House Counselor Ed Meese's words, "something that may not be desirable," millions of Americans have surged to the conclusion that it is abhorrent.

Fifty-eight senators have sponsored Jackson-Warner -- it is always safer to be with the commander-in-chief on such matters. Only three New England Republicans -- Lowell Weicker of Connecticut, Robert Stafford of Vermont and John Chafee of Rhode Island -- were bold enough to go on the real freeze bill. Several members of his party have chided Hatfield for "boosting" Kennedy by joining him. Kennedy, who was worked over vigorously by his constituents before he stepped out to lead the freeze, has been transformed by his advocacy. He has, said one of his eternal partisans, "captured the ultimate presidential issue."

The freeze following is one any politician would be proud to claim. It includes Billy Graham, Catholic bishops, Nobel scientists, eminent doctors, middle-class housewives, students and, in the countryside anyway, utterly respectable Republicans.

"There are none of those people who used to embarrass me in the early days of the antiwar movement," says Hatfield.

The pressure on Reagan, as one town after another rises up and demands a halt, is great. He knows that he is in a special position to bring about arms reductions. It is dangerous not just in itself, but because it encompasses his other prickliest issue, the economy.

It was explicit in the arms reduction question Helen Thomas put to him: "That way we can halt the making of doomsday weapons and save billions to help poor people."

He would, of course, save $4.2 billion on a seven-year civil defense program which some of the people charged with executing it regard as a joke. And then, of course, there is the $5.5 billion needed for the manufacture of the 17,000 additional warheads he regards as essential for our salvation.

From the freezers' point of view, the president could not have put their case better. He suggested the one thing they have gone beyond: the notion that a nuclear war is survivable. He simultaneously denied he believes that to be the case, but this is what he said: ". . . The Soviets' great edge is one in which they could absorb our retaliatory blow and hit us again."

This presupposes a first strike by the Soviets -- they might be tempted now they've heard they can "win" -- a response by us, after which there would be enough able and willing Russians left to stagger to their posts and fire another round on our smoking cities -- something serious students of nuclear aftermath say is not possible.

The real rage of the Reagan administration towards the freeze was perhaps expressed by Robert Michel, the Republican House leader, who took the floor after Speaker Thomas P. O'Neill had quietly appealed to Congress to choose "the path of life, not the path of catastrophe and annihilation."

Michel called the freeze "a proposal based on hysteria, cowardice, fear, pacifist dogma, misguided enthusiasm or geopolitical ignorance."

If Reagan had embraced the freeze, he would have smothered it. But he has given it new life. It is doubtful that he can be moved by grass-roots fervor. The real spur to arms control is his forthcoming trip to Europe. If he doesn't make some progress by then, he could set off demonstrations with a fallout he could never hope to recover from.