Senate Armed Services Committee critics of Paul C. Warnke get their opportunity to question his disarmament views today, but their cause appears to be lost.

The opposition that two weeks ago appeared to be building against Warnke's nomination to head the Arms Control and Disarmament Agency Control and Disarmament arms negotiator with the Russians lost its momentum.

"We were quite unsure how much opposition would be mounted," said one man who has worked for Warnke's nomination, "but it wasn't enough."

Warnke supporters predict there will be fewer than 30 votes against the nomination when the Senate votes. The Foreign Relations Committee will approve him today and the Senate vote could come as soon as Wednesday.

An important factor contributing to the confidence Warnke's supporters feel is that President Carter has been telephoning senators to stress the importance he attaches to the nomination.

Senate Majority Leader Robert C. Byrd (W. Va.), who earlier had said he wanted to hear the evidence and had spoken to reporters of opposition from a number of senators, last week predicted Warnke would get more than 66 votes.

"The Byrd statement was very important," one Warnke supporter said.

Another suggested that Byrd "wants to be with a winner."

The opposition formed a new group called the Emergency Coalition Against Unilateral Disarmament and distributed a packet of information critical of Warnke.

But nothing unraveled; the opponents have been unable to come up with an issue that would inflame anti-Warnke feeling.

"It's been a clean fight, cleanly won," said a man who is counting votes for the Warnke forces.

It appears that the steam also has gone out of the effort to deny Warnke his second hat as chief negotiator.

Gerard C. Smith, the last man to wear both hats, pointed out in a letter to Sen. Hubert H. Humphrey (D-Minn.) that when White House national security adviser Henry A. Kissinger was the chief negotiator the Congress was unable to obtain testimony from him since he was covered by executive privilege.

"I wonder if the proponents of severance of the two hats have considered that a repetition of that situation might be one result if their effort is successful," Smith wrote.

Sen. Henry M. Jackson (D-Wash.) was instrumental in splitting the two jobs during the Nixon administration and has many disagreements with Warnke.

However, Jackson has refused to commit himself publicly to voting against Warnke as has another advocate of stronger defense, Sen Sam Nunn (D-Ga.).

Without a publicly declared Democrat to lead the fight, the Warnke foes were seriously weakened.

The lack of support has forced opponents of Warnke to consider using a filibuster to block the nomination. Sen. Jesse Helms (R-N.C.) said yesterday that he would do "everything I can" to stop the nomination. Although he declined to use the term filibuster, he made it clear that the parliamentary maneuver was being considered by Senate conservatives.

Carter has given Warnke his full support, in contrast to the lukewarm backing he provided Theodore C. Sorensen's nomination to head the Central Intelligence Agency when that ran into trouble.

The Warnke nomination became a litmus test for Carter's often-declared intention to make a new strategic arms agreement with Moscow a high priority of his administration.

If the Warnke nomination were defeated, it would be a crushing blow to Carter's disarmament plans for it would demonstrate that the Senate overwhelmingly did not share Carter's sense of urgency nor his views on reducing strategic weapons arsenals.

However, despite the Armed Services Committee's unusual action in calling Warnke even though the Foreign Relations Committee has sole jurisdiction over his nomination, Carter appears to have paved the way for his nominee.

Jackson and others skeptical of Warnke's approach to disarmament can be expected to bring up their position on U.S. defense more powerfully on other occasions.