To preface this question, I have never actually played in a blackjack tournament. A player I know came to me with the following scenario and asked my opinion:

It is the final hand of his table and whoever has the most chips will move on to the next round. He is in the lead by $10. Both he and the second-place player have many times the table maximum in chips. So, the other player acts first on this last hand and bets the maximum. The player I know responds by also betting the maximum. He is dealt a 20 (T,T) vs. the dealer's 9 up. The other player acts first and flips over a hard 9 and doubles down. What is the play?