John B. Anderson is playing a nervous waiting game this week. He is waiting for the presidential debate, waiting for money, waiting for political magic to strike.

Forces, momentarily, are out of his control. He knows that. "All we can do this week is try not to fumble the ball," one traveling aide said.

So Anderson does what he can, Leisurely moving across the West, sometimes getting a cool reception, as he did today at the University of Colorado, where students at one point booed him and another yelled, "Cut the rhetoric. Talk about issues."

Each day he issues a statement on the great or near-great issues of the day -- on women in Portland, on conserving energy in Seattle and on solar energy in Denver.

But these things have little to do with how his independent presidential campaign will ultimately fare. Far more important are the debate and the negotiations Anderson's attorney, Mitchell Rogovin, is conducting with a group of New York banks for loans to finance the campaign.

Originally, campaign aides had hoped to get at least $5 million in cash to finance a major television blitz around Oct. 1. But now they have reduced their estimates almost by half. And it looks like it may be some time before they're even able to get that, raising doubts about when the ad campaign can begin.

The Federal Election Commission opened up the possibility for such loans with a recent ruling that Anderson's independent candidacy is the "functional equivalent" of a third party and that he is eligible for retroactive public subsidies if he receives at least 5 percent of the vote on Nov. 4.

For a bank to make a loan to the Anderson campaign, it has to satisfy a number of banking regulations and the federal election law. Under these regulations, banks have loaned large amounts of money to presidential candidates -- Jimmy Carter in 1976 among them -- but only in cases when the candidates' access to later federal funding was assured. Anderson is seeking an unprecedented type of bank loan, because he can only get federal funding if he wins 5 percent of the popular vote.

Anderson's backers talk as if this were assured, but conservative bankers are likely to think otherwise.And the penalties to a banker for taking a mistaken risk on Anderson could be severe.

The comptroller of the currency reminded officers of all federally chartered banks in a circular in February that loans can only be made to political candidates if "the credit is extended in the ordinary course of business and the terms are substantially similar to extensions of credit to non-political debtors which are of similar risk and size of obligation." In other words, no special breaks for politicians.

That would ordinarily mean that the borrower would have to post collateral or give other good cause to believe the loan would be repaid. This won't be easy for Anderson. A banker who granted a loan without firm assurance of repayment could be guilty of unsafe banking practices under federal law.

Moreover, a bank cannot contemplate a loan to a politician if it thinks the loan might have to be written off as a loss. This is legally impossible, because writing off such a loan would amount to an illegal campaign contribution.

If Anderson does get the bank loans as his campaign staff says it expects, they are likely to be expensive. The prime rate banks are now charging their best customers is more than 12 percent, and a banker couldn't give Anderson that preferred rate without violating the prohibition on concessionary rates to politicians. Anderson would probably be charged several percentage points more, banking sources said yesterday.

Rogovin said he sees no such problem in securing the loans, and he accuses Carter administration and campaign aides of starting a "whisper campaign" to undermine his efforts.

The collateral Anderson is offering, he said, are public opinion poll findings. The argument is that the polls indicate that Anderson is almost certain to get more than 5 percent of the vote and thus automatically be eligible to receive a federal repayment of $3 million.