Why does R. Akiba acclaim Bar Kokhba as messiah?

Peter Schäfer has argued that the name of R. Akiba is secondary to y. Ta'an. 4:8/27, in which R. Akiba is said to have acclaimed Bar Kokhba as messiah. Some interpreters have countered, however, that rabbinic haggadah would not attribute such an embarrassing position to R. Akiba if he had not held it. In response to both these arguments, I propose that the R. Akiba-Bar Kokhba tradition fits a pattern of talmudic stories about the Second Revolt in which the rabbis are anachronistically cast in a position of influence. This tradition is an example of a late antique literary topos attested in Jewish, Christian, and pagan sources in which a founder of a minority movement is remembered as having conversed with a contemporary world leader. In short, both Schäfer and his critics are right: R. Akiba was not originally part of the tradition preserved in y. Ta'an. 4:8/27, but there is a compelling tradition-historical rationale for inserting him there.