A close friend and former constituency party chairman, Canon Miles Raikes, said Mr Ashdown broke the news of his resignation to him on Tuesday.
He said: "My first reaction is gratitude for all that he has done for us both locally and nationally. When he came to this constituency we were in third place. Every seat in Somerset was held by the Tories, but now we have got most of them.
"Paddy's achievements have been absolutely colossal.
"My second reaction is this he has shown great wisdom in giving the party notice of his decision. He was thinking of the party as well as himself and that is typical of Paddy."
He added: "This is very much the end of an era."
Stephanie Bailey, vice- chairman of the constituency party said: "I think we accepted that he was going to step down sometime. Locally, we are pleased that we are going to have him back as our MP when he steps down as leader, although he has always been a very good servant to the town.
"Paddy has promised us that we are going to identify a successor and he is going to work closely with that person to enable the work that we have done to carry on."
The mayor, Roger Baker, said he believed Mr Ashdown would now take a back seat in public life. "I am as surprised as anyone to hear the news - Paddy will certainly be missed.
"He has worked hard to get where he is and obviously he feels now is the time to go. I really don't know what he will do but he will probably step back into the background.
"I think that is what this is all about - he wants a home life and he certainly deserves one after such a lot of hard work."
Nick Speakman, chairman of South Somerset district council and Mr Ashdown's agent during five general election campaigns, said he had pledged years ago to stop being an MP by the time he reached 60.
Mr Speakman said: "This is not entirely a surprise because Paddy confided in me some years ago that he would not remain an MP after he was 60.
"I think that for anyone to be the leader of a third party who does not have all the advantages and trappings of a Prime Minister or of Leader of the Opposition is a huge strain."Reuse content