PORTLAND,ORE. -- Eschewing any grand strategy and exploiting his mastery of bare-knuckled tactics, Republican Sen. Bob Packwood has been running the negative television ad against Rep. Les AuCoin he first used last spring to weaken AuCoin before the Democratic senatorial primary election.

The ad attacks Packwood's Democratic opponent as "a study in hypocrisy." When Packwood, running for his fifth term in the Senate, aired the spot just before the May primary, AuCoin looked like a fairly comfortable winner over Harry Lonsdale. The commercial cut his 8-point lead so severely it took a recount before AuCoin won by 332 votes.

In Oregon, the state that has long been a pioneer in progressive reforms, Packwood's ad symbolizes the descent of election-campaign politics into the gut tactics of negative campaigning that are chilling voters from California to New York. "No one in this state is going to vote because they are for a candidate," a Republican source told us. "They're all holding their nose."

Disembodied from the presidential campaign, Packwood is concentrating on tactical warfare with a sure instinct, probably sure enough to make him a close winner on Nov. 3.

He boycotted the Republican National Convention, but not just to publicize his scorn for the party's rigid antiabortion dicta and its foray into the politics of "family values." He wanted to sever any identification with a president whose standing here is so low that we found not one politician in either party who thinks Gov. Bill Clinton can lose.

The "hypocrisy" charge that Packwood believes to be so potent is aimed at AuCoin's absentee-voting record in the House (actually, not much worse than Packwood's in the Senate), his vote to raise congressional salaries, his frequent paid lectures outside Washington and the 83 checks he bounced in the House bank. A variation on this theme was Packwood's notorious "game show" spot, showing a facsimile of TV's "Jeopardy" with the hostess saying, "Welcome to Hypocrisy," and paying progressively higher amounts to contestants naming "congressional hypocrites" who always turned out to be Les AuCoin.

AuCoin has had his own bag of tricks. His low-blow TV ads attacking Lonsdale in the primary campaign so enraged his millionaire opponent that Lonsdale not only refused to endorse him but will encourage a write-in vote for himself. "I'm writing my own name in, and I'm asking friends to do the same," he told us. If he should back that up with advertising, it could cost AuCoin two or three precious percentage points or more.

Differences in degree separate the two candidates on most of the major issues in a state that has escaped the worst of the recession. Packwood's long pro-choice battle got him the endoresment of the National Abortion Rights League, but the state chapter endorsed both candidates. AuCoin is backed by COPE, the AFL-CIO political arm, but Packwood has some of the construction unions. Owls vs. woods, viewed from afar as a raging environmentalist battleground, offers political dividends to both from differing constituencies.

On trade, however, there is a sharp break. Packwood favors the North American Free Trade Agreement, a popular issue in this export-driven economy. AuCoin, faithful to labor's endorsement, opposes it.

Packwood's strategists aren't saying it publicly, but the senator sent an emissary to the White House two weeks ago to inform chief of staff James A. Baker and his campaign team that they are missing obvious opportunities to help Packwood -- and George Bush as well.

On the most important of these, Baker was urged to approve federal Medicare payments to Oregon barred by Washington because the state's "quality care" rule limits some treatment for the terminally ill. "Practically everybody in this state is for this," a Packwood aide told us. "It would lift the entire ticket." But no such relief is really expected from the White House given the present state of Bush's campaign and his perceived hopeless position here.

Packwood is on his own. The shrewd street-fighter who beat the unbeatable Wayne Morse way back in 1968 doesn't mind at all. In the capital, then chairman of the Senate Finance Committee, he drove the 1986 tax reform bill through Congress with a display of strategic brilliance. Out here, whatever the voters want, his role is different: the toughest alley cat in town.