Republican voting bloc exposed

James Fallows posted an interesting letter from a "someone with many decades' experience in national politics" explaining that Republicans now vote as a block for "structural" reasons.  These concern how the GOP selects its candidates.  Republicans can no longer be expected to side with Democrats on important legislation, lest they face a primary challenge from within their own party.   The American tradition of bipartisanship has become a pipe-dream.  Fallows comments:

If Democrats could find a way to talk about structural issues -- if everyone can find a way to talk about them -- that would be at least a step. And the Dems could talk about the simple impossibility of governing when the opposition is committed to "No" as a bloc.

That would be highly desirable.  But on what basis do we assume that the Democratic Party wants this problem solved? The myth of bipartisanship may be useful to its leaders.

On one hand, in terms of attracting voters, many Democratic politicians need to be seen supporting legislative initiatives that appeal to liberals.  On the other, the Democratic Party surely does not want to be blamed for actually having passed laws harmful to its donors.   It takes deep pockets to underwrite national and state-wide campaigns. 

If the myth of bipartisanship was exposed, Democratic leaders would face more pressure to herd Democrats to vote as a block.  This would create a dilemma: either alienate your financial base or your voter base.  

In a world where a handful of Republicans retains the power to vote down a liberal agenda, a Democrat doesn't have to.  Republican nay-saying, the filibuster, etc. means most Democrats can be seen to have voted the right way by their constituents.  Yet these votes need not happen at the expense of the Democratic Party's ability to attract wealthy donors.  Whilst  the public is none the wiser, politicians can have their cake and eat it too.