Like a born-again Bee Gee, Robert S. Strauss is rapping out his political disco on how a Carter victory is sure to come when, for a surprise finish, he cranks his baritone up to a shrill falsetto.

"It's gonna be the president because by Election Day, people will start really thinking . . . and when that happens, John Anderson will go "Poooofff !"

Somewhere, surely a glass is shattering -- is it Strauss or is it Memorex?

-- as the silver-haired chairman of the president's campaign pushes back from his desk, immensely pleased, and offers a series of fine, screeching encores. "Poooofff! . . . Poooofff! . . . Poooofff !"

In the chambers of the Carter-Mondale campaign, optimism abounds these days, unfettered by the numbers in the national polls, which so far show the president only even, at best, with his Republican challenger, Ronald Reagan.

It is an optimism that abounds despite the realization that an only-even poll does not, in fact, mean that Reagan and Carter are tied in the battle to win the 270 electoral votes necessary to capture the election. In fact, in most polls, Carter is ahead only in the South and trails in the other regions. And because electoral votes are captured in each state on a winner-take-all basis, most calculations have Reagan still significantly ahead in the contest for electoral votes.

The optimism in the Carter-Mondale camp abounds because of a conviction that Anderson's candidacy will fade away, and that his support will mostly return to the Democratic column, whence it came. It will be lured liberally back to the fold by appeals from Sen. Edward M. Kennedy (D.-Mass.), who will be campaigning in a number of urban areas on behalf of Carter.

It is an optimism that comes as well out of an almost gleeful feeling among Carter-Mondale officials that voters have serious concerns about Reagan's ability to handle the rigors and the complexities of the presidency -- concerns raised by Reagan's starting his campaign with a series of miscues (mostly minor) and then being placed carefully under wraps by his handlers, shielded from press questions.

Carter television commercials have been designed to draw a sharp, although unspoken, contrast between Carter's and Reagan's ability to work long and difficult hours.

And Carter drew a sharp, spoken contrast in a town meeting yesterday in Corpus Christi, Tex., between his ability to answer questions in public and Reagan's reluctance to do so.

And the Carter-Mondale optimism comes, finally, from a deeply held feeling, as comforting as Gospel, that Carter will win because -- more than anything else -- Carter always wins, always come back against great odds and adversity, often to the surprise of the experts and the pundits and that never-defined block that Richard Nixon used to talk of as "those who" (as in, "There are those who say . . .").

"Jimmy Carter always comes back," adviser Hamilton Jordan said confidently some weeks ago, back before placing himself into seclusion in the name of strategy-making. "It's as simple as that."

The Reagan campaign takes its comfort these days from the projections of its pollster, Richard Wirthlin, who says that the Republican nominee is still comfortably ahead in the state-by-state fight for electoral votes.

With 270 electoral votes needed to win, Wirthlin says his projections show Reagan with "a substantial number of electors more than 300." His last attempt to calculate a lead in terms of electoral votes was completed by the first of September, which was before the impact of that latest round of Reagan's campaign-opening slips. The survey took a detailed look at 17 key states, and then superimposed those results over a nationwide study in order to project national electoral vote standing.

"Our poll confirmed that we stand well in the electoral vote," Wirthlin said. His polling counterpart in the Carter campaign, Patrick Caddell, disagrees. Caddell offered no statistics to back up his view. However, recent Caddell surveys are largely responsible for the resurgence in the Carter campaign optimism, and they have caused the Carter officials to make some significant shifts in their campaign battle plan.

Before the fall campaign began, Carter adviser Chris Brown, who is now director of targeting and registration for the Democratic National Committee, prepared a guide that ranked the states according to the "percentage of effort" that the campaign should expend this fall.

It recommended highest-ranked efforts in New York, Pennsylvania, Texas, Ohio, Florida and North Carolina -- all of which Carter carried in 1976 -- plus top efforts in Illinois, Michigan and New Jersey, states that went to Gerald Ford four years ago.

The guide urged a lowered campaign effort in the nation's largest state, California, Reagan's home state, which went for Ford in 1976 and which Carter officials figured was destined to wind up as a Republican victory again in 1980.

It urged that the Carter campaign not waste time, effort and money on a state it did not figure to win. It urged reduced efforts as well for about 20 other western and smaller northern states.

But recent data from Caddell caused the president's strategists to alter significantly their plan as laid out in Brown's "Orange Book," according to senior campaign officials.

The Carter-Mondale effort in California will be sharply increased, the president's advisers insist. Caddell has reported that a recent poll showed Carter trailing Reagan by just 8 points in a three-way race in the state, and when Anderson was not included, the former California governor's home-state margin slipped to just 6 points.The latest California Poll of Mervin Field showed similar results, giving Reagan a 10-point lead over Carter.

"California is a late-moving state and there is a lot of softness there, a lot of float," said one senior Carter official. "It is also a state in which votes are moveable in huge numbers, very quickly -- they can be swung by media (television ads) and by events."

Caddell's surveys have prompted optimism on several political fronts, Carter officials say. As recently as last week, according to several senior campaign officials, Anderson's candidacy was still showing nationwide decline. They maintain that there is no indication that the president's refusal to debate Anderson in the initial campaign debate has created a sympathy backlash that works to the advantage of the independent candidate. In New York, Anderson has been losing support steadily among Jewish voters, Caddell's surveys are said to report, and those Jewish voters have been mainly going to Carter.

The Carter polling, like a recent New York Times survey, showed the president with a narrow lead in New York, according to campaign officials.

Winning New York is crucial to Carter's reelection prospects. Had Carter not carried the state in 1976, he would not have been elected president. Carter strategists conceded it is highly unlikely that Carter can be reelected without carrying the state.

Another critical finding in the Caddell polls so far is that the president is doing much better among Catholic voters in this 1980 contest with Reagan than he did among Catholics in 1976 against Ford. Caddell has calculated that overwhelming Ford margins among suburban Catholics gave Ford Connecticut and Illinois in 1976, and now, the pollster has reported Carter's prospects in both states are much improved. This is especially true in the heavily ethnic Catholic suburbs of Connecticut, the president's advisers say. In Connecticut, Reagan is viewed as even more of a "cultural dissident," than is Carter, according to one of the president's advisers.

Carter officials had hoped to be able to divert several of the large states that went for Ford in 1976 to their column in 1980. They are concentrating, in this effort, in New Jersey and Connecticut in the East, Illinois and Michigan in the Mideast, and Oregon and Washington in the West. They now consider their prospects in Illinois and Connecticut "excellent." A Chicago Tribune poll released Sunday showed Carter with a narrow edge in Illinois but with a large number of voters still undecided.

Carter may need to make these roads into 1976 Ford states in order to hold his own in 1980, because the president has several significant problems in the southern states that were his bedrock in 1976, even though he does lead Reagan in overall percentages for the region.

Florida, the largest state in the South, is the most important battleground in the region. Carter strategists rate the state as a tossup. And at this, they are figuring that the president is much better off than he was a few weeks ago, when his aides calculated him to be in serious trouble. The Cuban-American vote is expected to be overwhelmingly Reagan's.

Mississippi and Louisiana have both been considered by Reagan officials as southern states destined to return to the Republican presidential column in 1980. Carter officials concede this is a distinct possibility, but say their figures show the president's fortunes improving, at least in Louisiana.

Both camps concede that Reagan is ahead in Virginia, the only southern state that did not vote for Carter in 1976. South Carolina is considered to be very close.

As the Carter officials pursue their strategy of trying to shore up their southern base and probe for Reagan weaknesses, they have convinced themselves, above all, that they will be all right in the end as long as they do nothing to boost the candidacy of Anderson.

So it is that they are convinced of the correctness of their decision to exclude Anderson from a Carter-Reagan debate to limit his exposure as a serious candidate. And they are convinced that the public understands and accepts the decision.

"People know that Reagan, Anderson and Carter all have political reasons for taking their positions on the debate," says Strauss. "And they know that there's not a noble position in the bunch. There's nothing evil about it, there's nothing noble about it . . . It's just politics."

EPILOGUE: One of the major innovations of the president's fall campaign has been the institution of daily 8 a.m. strategy sessions, chaired by Hamilton Jordan and attended by what one official called "all of the thinkers and doers" of Carter's White House and campaign.

The idea is to anticipate each day's problems and map out a daily strategy for dealing with them. "It works great," Strauss says. "Every morning at 8 we set our strategy. And that strategy lasts 'til about 10 a.m. -- and by then everyone's going into business for himself.

"The main result is I now talk to Jody Powell about five times a day. Some say he's sick of me. Well if he is, it's mutual."