WHILE CONTINUING to insist that he is still in hot pursuit of the 1980 Republican nomination Rep. John B. Anderson of Illinois is publicly agonizing over running as an independent presidential candidate in November.

Mr. Anderson has revealed that he would commission a public opinion poll with the expressed hope of proving that his third-party run would not simple result in the election of former California governor Ronald Reagan as president. The always interesting conventional wisdom now holds that an independent run by Mr. Anderson would attract those who would be more likely to vote for President Carter, in a two-man race, than for Mr. Reagan.

Obviously, the supporters of the president are among the subscribes to the conventional wisdom, because the general counsel of the Carter-Mondale reelection committee disclosed last week that its attorneys are checking the election laws in all 50 states in order to be able to challenge legally, if necessary, Mr. Anderson's attempts to be listed on November ballots.

But Mr. Anderson is not without his own legal team. Stewart Mott, the General Motors heir and financial angel of liberal causes, has organized a team of election-law experts, one of whom, John Armor of Baltimore, is confident that Mr. Anderson could win listing on the ballots of states with 90 percent of the electoral votes. Mr. Armor is no Johnny-come-lately to third -party endeavors, having worked in the independent campaigns of former Georgia governor Lester Maddox and former senator Eugene McCarthy. f

Mr. Mott is a longtime critic of the Federal Election Reform Act (which Mr. Anderson sponsored in Congress), the law limiting any individual's contribution to any federal candidate to $1,000. Mr. Mott has already spent, by his own reckoning, about $85,000 in behalf of Mr. Anderson's candidacy. Those expenditures have been independent of the Anderson campaign and therefore are a totally legal exception to the Act. Mt. Mott is not finished in his support of John Anderson; he states publicly that he can be counted on for another $50,000 to $100,000.

What cannot be counted on by Mr. Anderson and his allies are the state laws of Maine, Kentucky, New Jersey, North Carolina and Massachusetts. For listing as a third-party candidate in November, Maine required 4,000 signatures on petitions by April 1. Kentucky wanted 5,000 signatures by April 2. The Anderson forces met neither state's deadline. Massachusetts law insists on the submission of 39,245 signatures by May 6. A New Jersey ballot position is available only to those candidates who have submitted 800 signatures of voters by April 24. But North Carolina is the real challenge to anyone committed to a third party. By April 25, the Tarheel State wants the individual signatures of 166,377 voters. If past experience in these matters is a reliable guide, any third-party candidate had better have 40 percent more signatures than the statutory minimum in order to defeat challenges.

So, gone is the "Anderson Difference" of his earlier campaign commercials, replaced by the Anderson Dilemma. Will he or won't he? Can he or can't he? While a recent national poll indicates that 58 percent of the voters are dissatisfied with an election between Mr. Carter and Mr. Reagan, Mr. Anderson agonizes -- and time continues to run.