Does Influence = Leadership?

Matthew 16.5-12:
When they went across the lake, the disciples forgot to take bread. “Be careful,” Jesus said to them. “Be on your guard against the yeast of the Pharisees and Sadducees.”
They discussed this among themselves and said, “It is because we didn’t bring any bread.”
Aware of their discussion, Jesus asked, “You of little faith, why are you talking among yourselves about having no bread? Do you still not understand? Don’t you remember the five loaves for the five thousand, and how many basketfuls you gathered? Or the seven loaves for the four thousand, and how many basketfuls you gathered? How is it you don’t understand that I was not talking to you about bread? But be on your guard against the yeast of the Pharisees and Sadducees.” Then they understood that he was not telling them to guard against the yeast used in bread, but against the teaching of the Pharisees and Sadducees.

It would seem that the idea of "yeast" would be that of influence: the teachings of the Pharisees, their way of thought...

But then later in Luke, Jesus says this:

Luke 12.1-3:
Meanwhile, when a crowd of many thousands had gathered, so that they were trampling on one another, Jesus began to speak first to his disciples, saying: “Be on your guard against the yeast of the Pharisees, which is hypocrisy. There is nothing concealed that will not be disclosed, or hidden that will not be made known. What you have said in the dark will be heard in the daylight, and what you have whispered in the ear in the inner rooms will be proclaimed from the roofs.

Here, the yeast is labeled as hypocrisy.

This seems consistent with Paul when he says:

1 Corinthians 5.6-8:
"Your boasting is not good. Don’t you know that a little yeast works through the whole batch of dough? Get rid of the old yeast that you may be a new batch without yeast — as you really are. For Christ, our Passover lamb, has been sacrificed. Therefore let us keep the Festival, not with the old yeast, the yeast of malice and wickedness, but with bread without yeast, the bread of sincerity and truth."

But here is the one that best deals with yeast as a metaphor for influence, also from Paul:

Galatians 5.7-10:
"You were running a good race. Who cut in on you and kept you from obeying the truth? That kind of persuasion does not come from the one who calls you.
'A little yeast works through the whole batch of dough.'
I am confident in the Lord that you will take no other view. The one who is throwing you into confusion will pay the penalty, whoever he may be."

That one really nails it. Influence is a powerful force, and in some cases, a dangerous one.

There is, however, a passage that sees this form of influence in a more positive light:

Matthew 13.33:
He told them still another parable: “The kingdom of heaven is like yeast that a woman took and mixed into a large amount of flour until it worked all through the dough.”

The Kingdom of Heaven works the same way... Here I am reminded of the very first passage listed above. What did Jesus do with 5 loaves and 2 fish? He multiplied them! His working power worked through what was there and it was multiplied. Awesome... Likewise, Jesus invested in 12 men and several women... fast-forward 2,000 years -- we are here. A little worked through the dough producing amazing results.