Look for Ronald Reagan to return to basics during the upcoming fall campaign, even as he is departing from them while promoting his $98.3 billion tax increase bill. While the details have yet to be decided, the broad themes of Reagan campaign strategy call for the president to point with pride at falling interest rates and a declining rate of inflation while blaming the Democrats for the underlying economic malaise that has produced record postwar unemployment and runaway deficits. And all this at a time when the president is relying on Democratic votes to win approval of his tax increase.

"Basically, we're tapping the old anti-Washington sentiments that have always been central to Reagan's appeal," acknowledges one strategist who remembers how Reagan, as governor of California, inveighed against the "puzzle palaces on the Potomac." But President Reagan lives in one of them now.

One idea that has been kicked around in the inner councils is a proposal to keep Congress in session during October, as president Harry Truman did with the celebrated "do-nothing" Congress that became his steppingstone to the upset victory of 1948.

The idea behind the Reagan variant of this strategy would be to dramatize congressional inability to agree on a budget or additional spending cuts. Strategists who favor this plan are confident Reagan could veto any continuing resolution to keep government going, forcing Congress to approve a budget on terms acceptable to the president.

But don't bet that this drawing-board strategy will ever be put into place. It has run into determined opposition from Senate Majority Leader Howard H. Baker Jr. (R-Tenn.), whose leadership and cooperation is vital to the administration. So, Reagan will probably let Congress go its way and campaign against the institution just the same.

Gloomily forecasting defeat on the upcoming tax increase bill he steadfastly opposes, conservative fund-raiser Richard Viguerie offered this comment: "Never underestimate the ability of a Republican president to roll Republican congressmen" . . . . One conservative GOP congressman refers to the measure as the "Baker-Stockman-Darman exit bill," referring to right-wing hopes that defeat of the measure would be a prelude to the departure of White House chief of staff James A. Baker III, Office of Management and Budget Director David A. Stockman and presidential assistant Richard Darman. At least in the short run, this is wishful thinking . . . .

In another triumph of political newspeak, Reagan managed to deliver his 30-second televised promo for his tax increase without mentioning the taboo word "taxes." What was once "revenue enhancement" has now become an otherwise unidentified "building block" of the economic recovery program.

House Speaker Thomas P. (Tip) O'Neill Jr.'s invitation to Reagan to make his televised address for the tax increase bill before a joint session of Congress never received serious attention at the White House. The administration view was that Democrats would use the occasion to refrain from applause and make the televised point that the bill is Reagan's idea, not theirs.

In the wake of Murray L. Weidenbaum's departure as chairman of the Council of Economic Advisers, some memos are circulating that suggest again that Reagan was given a rosier view of 1982 economic prospects than the facts have warranted. Weidenbaum was known among insiders as one of the few administration officials willing to speak up and give the bad news directly to the president. But his Jan. 5, 1982, memo to the president on the state of the economy is full of cheer, starting out with the bromide that "the night is always darkest just before the dawn" and saying that "the basics for a spring recovery remain in place."

This memo, far from unique, points to what some insiders believe is Reagan's biggest problem, namely the unwillingness of his advisers to tell him the bad news. Even with frank advice, natural optimist Reagan tends to believe that everything will turn out for the best.

Boosters of California Republican gubernatorial nominee George Deukmejian, including former White House speech writer Ken Khachigian, are trying to persuade the White House staff to schedule a separate Reagan fund-raiser for their candidate. The current Reagan schedule during the president's upcoming trip to California limits Deukmejian to the proceeds of a reception that will precede a fund-raising dinner the president will hold for GOP Senate nominee Pete Wilson on Aug. 23 in Los Angeles . . . . White House counselor Edwin Meese III showed up at a senior staff meeting last week wearing a button that said "Unmuzzle Rollins," a reference to an ill-timed order by chief of staff Baker instructing political director Ed Rollins to keep his candid views to himself until after the Nov. 2 election. The entire order has become somewhat irrelevant anyway since the return to the White House of Lyn Nofziger, a man who has never been easily muzzled.