Just look at their choices. See if you agree.  We don't. The Brits must 
have a totally different definition of "Liberal" - and have no clue as 
to who is influential in the US and who is irrelevant.  They list Joe 
Lieberman and Chris Matthews as 'liberals' - for starters - and need 
some real help in correcting their political acumen of life across the 
pond.  You can ad your own 'most influential' liberal or conservative to 
their list.  Go for it.

http://tvnewslies.org/tvnl/index.php/latest-news-at-a-glance/political-glance

UK - Telegraph article:

The 50 most influential US political pundits
Monday, 28 April 2008 14:48

With the internet revolution and the growing popularity of cable 
television, the multitude of voices can seem be bewildering and, 
occasionally, deafening.

The Daily Telegraph today unveils its list of the 50 most influential 
political pundits to help readers sort through whose opinions matter. 
These are the people who make voters sit up and take notice. They are 
the ones who political candidates and campaigns are constantly seeking 
to woo and influence. They include television presenters, newspaper 
columnists, bloggers and talking heads.

More...