Gandalf got it wrong when he let the matter of the Ring rest. When he confirmed that Frodo's ring was the One, he should have sent Frodo to Rivendell straight away before meeting with Saruman. True, it would have meant uprooting the young hobbit, but his failure to do so meant that the Nazgūl came within a hair's breadth of recovering the Ring. On the other hand, the delay allowed Merry and Pippin to cotton on, and tag along. If you believe that this was the all-important plus side to Gandalf's procrastination, you might want to click
here.