This final stump speech was not precisely Mr. Perot's last words of the 1996 campaign: tonight he appeared in prerecorded prime-time infomercials on ABC, CBS and NBC. But the address here all but brought to a close several weeks of intensified barnstorming by a wealthy political maverick who in the past had depended almost wholly on infomercials, televised interviews and debates to reach voters. His exclusion from the Presidential debates this year and his inability to buy all the infomercial time he wanted led him to employ the techniques he had long decried: stump speeches and grip-and-grin politics. During a part of the speech devoted to what he characterized as the President's moral and ethical lapses, Mr. Perot seemed to acknowledge the probability of a Clinton victory. ''Isn't it incredible,'' he said, ''that we have someone like that who may be elected, or re-elected, as your President? With that thought in mind, we paid $1 million for one hour of network time tonight.