Just over two years ago, the presidential ambitions of Sen. Robert J. Dole (R-Kan.) collapsed in New Hampshire after a devastating television assault by then-Vice President George Bush, who portrayed Dole as "Senator Straddle," an equivocator who could not be trusted to hold the line against tax increases.

An angry, embittered Dole returned to Washington to face what he now acknowledges was a difficult year. When Bush was sworn in as president, Republicans at both ends of Pennsylvania Avenue braced for a fireworks display of retaliation from the proud, prickly Republican leader of the Senate.

It never came.

Instead, Dole became the president's foremost ally on Capitol Hill, suppressing any temptation for revenge as he helped Bush rack up a series of political victories in the Democratic-controlled Congress, including an unbroken string of 10 sustained vetoes.

He bit his sharp tongue and seldom strayed from the Bush line, even on issues such as the federal budget and U.S. policy toward China, on which Dole has staked out more aggressive positions in the past.

Acknowledging that age will probably bar another bid for the presidency in 1996, when he would be 73, Dole has thrown himself back into his Senate work, branching out more into foreign policy and taking controversial stands on issues such as aid to Israel. During congressional recesses, when he isn't on a foreign trip, he is campaigning for Republican Senate candidates, and friends say he has now set his sights on a GOP takeover of the Senate in 1992 and a capping of his political career as majority leader.

"From my vantage point, the president should be well pleased with the way Dole is conducting things as Republican leader," said Senate Majority Leader George J. Mitchell (D-Maine), who engages in daily combat with Dole, the president's point man in the Senate.

"Bob really has gone to the mat with us to say, 'This is one the president really wants,' " said Minority Whip Alan K. Simpson (R-Wyo.). "It's the real pro in him. . . . The proof is in the delivery, and Bob Dole has delivered."

Memories of New Hampshire linger, however.

Asked how he feels now that Bush will be relying heavily on "Senator Straddle" to help reach a budget compromise with the Democrats that many believe will include tax increases, Dole smiled broadly and said, "I think it's called irony."

To a friendly audience, he joked recently that he may ask New Hampshire for a recount.

While these remarks indicate that Dole may not have forgotten, they are a far cry from the withering retorts that have long been his political trademark. Eighteen months into the Bush presidency, colleagues describe relations between the two men as unfailingly polite, somewhere between correct and cordial. "Quite businesslike," says Mitchell, who meets frequently with both men at joint leadership sessions at the White House.

Despite Bush-Dole generational bonds and their years of association in Republican politics, there was a vast distance between the manicured lawns of the Bush estate in Greenwich, Conn., and the cornfields of Russell, Kan., where Dole grew up, that the two men never bridged, according to senators who are friends of both. The bitterness of their clash of presidential ambitions, more so for loser Dole than winner Bush, has made even trust a major achievement.

Sitting in his Capitol office, which commands a sweeping view of the Mall as it leads toward the White House, Dole recently discussed his relations with Bush with a mix of caution and candor, lifting the curtain only fleetingly on his feelings about the president.

"I think we have a good relationship, but obviously it {took} a while for those things to heal over," he said. "Some things were said. . . . " he continued, never finishing the sentence.

Dole conceded that "there was a period of time early when the White House was not certain about Bob Dole, whether he could deliver." But "I think that was sort of laid to rest during the Tower nomination" fight, he added in reference to his relentless, although losing, battle to win Senate confirmation of former senator John G. Tower (R-Tex.) as secretary of defense early last year.

As of now, "I don't think the president or anyone in the White House has any trouble with me," Dole said, although some White House aides continue to express apprehension about Dole's motives and dependability in a crunch.

His New Hampshire defeat has "got to eat away at him," said Sen. Warren B. Rudman (R-N.H.), who managed Dole's campaign in the state. "That wasn't just a bitter experience, it was devastating. To come out of Iowa {where Dole won}, to come to New Hampshire with huge crowds at the airport, to tour the state for five days and to be told you're ahead in the polls and then to get hit with that tax stuff and then see it all dashed -- that's tough." Rudman said.

In the year following the New Hampshire primary, "I think Bob was more quiet, more restrained, obviously deeply affected by the experience. But he sure has bounced back. . . . Now he's the old Bob Dole," Rudman added.

According to Republican lawmakers, both Bush and Dole have gone out of their way to repair their relationship with personal gestures of solicitude. When the Senate early last year sustained Bush's first veto of a bill -- the measure guaranteeing U.S. residency to Chinese students -- Dole dispatched an aide to get the vote tally, signed it with a warm personal note and sent it to the president as a trophy of victory. "George {Bush} was quite touched by that," said Simpson.

Months later, when Bush heard that Dole's sister was undergoing chemotherapy in Kansas, Bush called the Republican leader to offer the services of his personal physician. "I thought that was very thoughtful, very nice," said Dole.

After Mitchell unleashed an attack on the president's policies toward China late last month, Dole got in touch with Bush almost immediately, and Bush responded with appreciation the next day. But in a kind of metaphor for their relationship, they communicated by faxed letters.

To those who know Dole best, his self-discipline and resilience is no surprise.

Almost all cite the nearly four years of painful recuperation from World War II wounds, which nearly cost Dole his life and crippled his right arm, as a source of Dole's relentless drive and strength in hard times. "Cable steel," Simpson calls it.

"Bob's been through plenty in his life. Talk about disappointments, he's had them," said Sen. John H. Chafee (R-R.I.), chairman of the Senate Republican Conference.

Dole has shown a recent preoccupation with foreign affairs, approaching daunting problems such as hostilities in the Middle East with the disarming simplicity of trying to cut a deal on a tax bill in the Senate, some say. He has been drawn to the Middle East out of hope he could somehow help produce peace in the region, they say. When Simpson asked him why the Middle East, Dole responded, "What's to lose?"

Simpson tells a story about their recent trip to the the region, when Dole's group met with Iraqi President Saddam Hussein, who spoke at length about the suffering of his country in the Iran-Iraq war. At the end, Simpson recalled, Dole said, "I've never spoken personally like this, but do you see this arm?" and he gestured with his withered right arm. "I have this daily reminder of the futility of war," he said. "That's why we're here." Even the Iraqi leader sat in stunned silence, Simpson said.

In Israel and among Jewish groups at home, Dole created a furor with his proposal for across-the-board cuts in aid to Israel and other major U.S. aid beneficiaries and his suggestion that Jewish leaders are behaving selfishly in opposing such a cutback. He added to the controversy by repudiating a Senate resolution proclaiming Jerusalem the capital of Israel.

Dole said he stands by these assertions and many senators, privately commend his courage for taking on the pro-Israel lobby while lamenting some of his sharp rhetoric.

What about another run for the presidency? "I don't think it's possible. Age gets to be a barrier. . . . I gave it my best shot," Dole said matter-of-factly. "But I think being the leader {in the Senate} is pretty important," he said, his eyes brightening. "What we're trying to do now is change one word: from minority to majority."