What becomes the "center" changes over time.  We all know that because we've seen it move rightward for decades now.  

While many denizens consider "centrist" as inherently an epithet, successful social movements help redefine what the "center" is.  So long as a measure that is advocated is seen as marginal, as lacking in broad-based support, it stands no chance of being enacted.  

What is "centrist" is not the same as what has broad-based support.  This seems to be one of the prevalent false assumptions of our day.  All the proponents of the status quo have to do to cow many elected officials into backing down, apparently, is to rhetorically capture the political center by claiming it for themselves and in so doing labeling meaningful steps to deal with, say, jobs and regulating Wall Street, as not "centrist" but as "far left" or "radical" or coming from "the angry left".

"Center" means what whomever succeeds in claiming it wants it to mean.  It tends to carry connotations in our political dialogue of being presumptively "mainstream" and "sensible", and  presumptively commanding of broad public support, although this is simply not the case on many policy issues where the public has a long record of saying what it believes and wants.  

Ceding the "center" rhetorically is an enormous and common mistake people who think of themselves as liberals and progressives make when public opinion is actually on their side.  

Action on both jobs and financial reform is right now broadly desired by the public.  It is seen as in no way "radical" or "non-mainstream", but, to the contrary, indicative of being responsive to Main Street and not just Wall Street.  (Why do you think even some right-wing Republicans such as Richard Armey are seeking to muddy the waters by making it sound as though they, and not the Democrats, are the party that is most committed to acting on these issues?)  

Where public consciousness and opinion broadly supports actions that are being demanded, competent public officials should be able to define to their publics--if they want to--the changes being called for as "centrist".  

And Presidents usually want to.  My observation is that this President appears to want to define measures he takes as "centrist" wherever he can.  We heard evidence of this just last week at the nationally televised meeting with the Republican House members when, citing Bob Dole and Howard Baker's support for something similar to the health care proposal now on the table, he referred to that proposal as "pretty centrist."  

Translation: "mainstream", "safe", "not scary", etc.  There are many built-in advantages to being seen by the broader public--not so much with activists, and thus a rub--as doing something "centrist".

This is the battle for public opinion--and with it the opportunity to define the public debates in our day--in a nutshell. When progressive measures are popular and can be "marketed" as "centrist" this should count as a victory for many of us.  It means the center has actually been moved leftward.