Think tanks and policies: Nick Pearce and Karen Lumley
17 September 2012 Last updated at 12:25 BST
No-one votes for them but the men and women who work for political think tanks do have an effect on political life in Britain.
They come up with bright ideas which can help shape party policies, which means either they are a vital part of democratic life or a bunch of theorists who should get out into the real world a bit more.
David Thompson spoke to Institute for Public Policy Research director Nick Pearce who explained what they do, and Conservative MP Karen Lumley who said her voters think she should come up with her own ideas.