But if in their view, at the time, they believe that someone MAY have a shot a being elected President, the likelihood is very strong that that person would be included in the debate. There is no exact standard of judgement, to the best of my knowledge. There is a Commission on Presidential Debates, that was established a few elections ago, and this commission, from 1988 and including 1992, has been responsible for organizing the debates. The commission is led by two co-chairmen. One is a former chairman of the Republican National Committee, Frank Fahrenkopf, and the other is a former chairman of the Democratic National Committee, named Paul Kirk.
Polls are more important now.
Polls have had a profound impact on campaigning at every level. If you're running for mayor of Boston, polls are crucial. If you're running for President, polls are equally crucial. If you have high polling numbers, the press and television will spend a lot of time covering you. Fundraisers will have less trouble raising money for your campaign.