WASHINGTON--A Democratic senator said yesterday he had seen Defense Secretary-designate John Tower "under the influence of alcohol" in the Senate, while another Democrat became the second to support the embattled Tower's confirmation.

Dennis DeConcini (D-Ariz.) commented just hours after President Bush insisted that "not one" senator had first-hand evidence that Tower had a drinking problem.

Meanwhile, Senate Majority Leader George Mitchell (D-Maine) flatly predicted the nomination would be rejected when it came to a vote, which he said he hoped would take place this week.

But a few hours later, Sen. Christopher Dodd (D-Conn.) pledged to support Tower.

"I owe John Tower the same fairness and careful judgment he used 22 years ago," Dodd said, referring to Tower's 1967 defense of Tom Dodd, then a senator and the father of the current senator. The elder Dodd was censured by the Senate for improper use of campaign funds.

In a riveting exchange on the fourth day of increasingly heated debate over Tower's personal qualifications, DeConcini said he saw Tower "under the influence of alcohol" while on the Senate floor. Tower served in the Senate from 1961 to 1984.

"But inebriated to the point that he could not operate?" interrupted Sen. Arlen Specter (R-Pa.).

"I have not seen him inebriated to the extent he could not perform his duties," replied DeConcini, who said later he had seen Tower "under the influence" several times.

But Tower, in a statement, denied the charge, saying, "I have never been inebriated on the Senate floor."

Bush, in a session earlier yesterday with White House reporters, repeated his insistence that no senators had first-hand information that Tower was hampered by a drinking problem.

"I haven't had one single senator--not one--[who] served with him over the years, say, `I have seen him. My first-hand evidence is this man is ineligible because of his consumption of spirits,'" Bush said.

Bush also defended Tower's vow that he would never take another drink if confirmed. "John Tower has said he'll never touch another drop of liquor and he'll have 25,000 people at the Pentagon making sure he keeps his word. I would say we have a fail-safe guarantee," Bush said.

Mitchell said that despite the decision Monday of Southern Democrat Howell Heflin of Alabama to support Tower, the nomination will go down in defeat.

"I believe that when the vote occurs the nomination will be rejected and it is obvious if the Republicans had the votes they would now be demanding the vote take place," Mitchell told reporters.

"I frankly see no benefit to anyone...in unnecessarily and needlessly prolonging this matter," he said, commenting before Dodd's announcement.

Meanwhile, Senate minority leader Robert Dole (R-Kan.) charged that Armed Services Committee Chair Sam Nunn (D-Ga.) has begun an unnecessary investigation of Tower. Nunn responded to Dole's complaints by explaining there were "three or four new allegations" about Tower and that Nunn had consulted with other Republicans before dispatching investigators.

Mitchell said also that he wants a confirmation vote soon, "certainly this week," although Republicans have spoken of prolonging debate through Easter.

But Dole said, "This has just barely started."