Deal or No Deal Odds

In the American version of Deal or No Deal, what are the odds of a contestant eliminating the entire left side of the board at any time during the game, before receiving the last bank offer (2 cases left)?

In case you don't know, there are 13 different amounts of money on the left side, and 13 different amounts of money on the right side.

Thank you in advance for your assistance!

This is the same as having the two remaining cases be from the right side. Even if a deal is made before reaching the last two, if all 13 of the left side briefcases are gone, the last two would both have to be from the right.

There are C(26,2) = 325 possible pairs of briefcases for the last two, of which C(13,2) = 78 are both from the right side, so the probability is 78 / 325, or 24%.