Bob Packwood has been on the quest for power for almost 20 years, since he was a young member of the Oregon house of representatives plotting his 1968 race against the legendary Sen. Wayne Morse.

Now he has power, and the Republican chairman of the Senate Finance Committee sits serenely in his office, wearing a blue cardigan and a perpetual Cheshire-cat grin, and lets everything come to him.

Money, for one thing; the tax bill, for another. At mid-year, Packwood reported $2.4 million cash on hand for his 1986 reelection race in a state with barely a million voters. By year's end, his hoard will have grown by at least another million, maybe to $4 million -- unprecedented sums for squeaky-clean Oregon politics.

It's not hard to raise when you're sitting in Packwood's seat. Last summer, Los Angeles businessmen and lawyers eager to get the word on taxes poured in $500,000 for the privilege of dining with Packwood. What they heard, one said bitterly, was "a sermon on leadership," a speech a Packwood aide laughingly said "200 Oregon high schools have gotten for free."

One fine day this fall, without Packwood's stirring, the House of Representatives will deliver its version of tax reform to his committee doorstep, and then President Reagan's No. 1 legislative priority will be in the hands of the man who may well have earned the title of the White House's least favorite Republican senator.

It's an old saying in politics that what goes around comes around, but for Packwood the turn of the wheel is indeed delicious.

Four years ago this month, Packwood was leading a bitter fight to block Reagan's plan to sell AWACS radar reconnaissance planes to Saudi Arabia. A few months after he lost that battle, he angered the president again by telling a reporter that in meetings with senators, Reagan often tells irrelevant anecdotes and "(we) just shake our heads."

There were more fights, including a battle on abortion in which Packwood said Reagan's stance was "driving one more nail in the coffin" of the GOP. In December 1982, with Reagan's close friend, Sen. Paul Laxalt (R-Nev.), in the lead, Senate Republicans punished Packwood for his "disloyalty" by stripping him of the chairmanship of the Republican Senatorial Campaign Committee.

After that rebuff, he went on tour through the eastern primary states to battle "for the soul of my party," against White House policies that he said were alienating women, labor, environmentalists, Jews and blacks.

And then in 1984, the reshuffle of Senate leadership allowed Packwood to move up to the Finance Committee chairmanship, which is one of the three or four genuine power centers on Capitol Hill.

His history, as much as his expressed view on assuming the chaip that "I sort of like the tax code the way it is," has led many people to conclude that Packwood's Finance Committee will be the burial place of Reagan's tax reform dreams. But the smiling man in the blue cardigan with the bulging bank account says the cynics have it all wrong. "If the House passes a bill," he told me last week, "we will pass a bill."

Why this unhedged prediction? Does he sense a public demand for tax reform that other legislators say is missing among their constituents? No. In Oregon, as elsewhere, "the public is not interested. You could support it or not, and it wouldn't make much difference."

Why will it pass, then? "The president wants a bill badly and he is entitled to one. He will get it. Whether it's a bill he likes, I don't know, but he will get a bill. You look at history, even with opposition Congresses: whenever a president has wanted a tax bill, he's gotten one."

Is this easygoing exponent of presidential prerogative the same Bob Packwood who defied -- and denigrated -- Ronald Reagan through the first term? Has he had a gland transplant?

Oh, no, he says. On some provisions -- such as employee fringe benefits and timber tax treatment -- he has warned the administration he will fight. Treasury accommodated his wishes on the first issue, not the second, which is vital to his Oregon constituents. So there will be a fight. And, he smilingly insists, there will be a bill.

Is this an elaborate charade, a prelude to legislative sabotage? I don't know, but Packwood is a puzzle of many parts these days -- even to one who has covered him from the first challenge to Morse.

Why the huge bankroll, which has raised eyebrows and drawn editorial criticism in Oregon? He speaks of an expensive primary fight with an anti-abortion right-winger and a tough general election battle in a state where Reaganomics has left the economy ailing. But the fact is that as of now, no credible opponent is in the race for either the primary or general election.

Is he banking money for a 1988 presidential bid to "save the soul" of the GOP, as rumor suggests? "I can't picture myself doing that," he says.

It's all so innocent. Not a hint of any desire for power or revenge. Bob Packwood would have you believe that the quest is over, that he's perfectly content with what he has, is eager to deliver the tax bill the president wants and is more than willing to let others battle over the future of the GOP.

We shall see.