Mark 11:30-33

Mark 11:30 (KJB)
The baptism of John, was it from heaven, or of men? answer me.

Then Jesus asks them the one question which will literally box them in. He focuses them back on the baptism of John. Was it something ordained of Heaven or was it something designed by men?

Mark 11:31 (KJB)
And they reasoned with themselves, saying, If we shall say, From heaven; he will say, Why then did ye not believe him?

Then the religious leaders went into conference and began to discuss it thoroughly. They may not have liked Jesus at all, but He did ask questions which would make them think and they knew they had to answer correctly or He would have them cornered again. They knew that if they responded that the baptism of John was from Heaven, then they would be asked why they did not believe it? It would make them look like unbelievers in front of all the people and that would cause them problems.

Mark 11:32 (KJB)
But if we shall say, Of men; they feared the people: for all men counted John, that he was a prophet indeed.

Then they discussed the other side of the question and that was if they told Jesus that the baptism of John was of men, then the people might stone them because the people held John to be a prophet. So it was the kind of question they would not be able to answer because either way, they were caught by their own unbelief.

Mark 11:33 (KJB)
And they answered and said unto Jesus, We cannot tell. And Jesus answering saith unto them, Neither do I tell you by what authority I do these things.

Since they knew if they answered the question in any direction, they would be in trouble with the people. So what they did was they had decided to take the easy way out and claim that they did not know the origin of the baptism of John. They were not ignorant of Johnís ministry but they wanted to get out of the situation which could have caused them much consternation. Now, because they answered in this fashion, Jesus then tells them that He will not tell them by what authority He has cleansed the temple. Now they not only had John to reckon with but now the ministry of Jesus. If they deemed John to be a prophet, then they would have had to believe his message, especially about Jesus being the Messiah. This was something they could not take a chance on.