Sure, a Democratic Senate sans-filibuster could pass legislation that might make a Republican House or president uncomfortable, and would be able to prevent its most vulnerable members from casting difficult votes (Blanche Lincoln, for example, would not have had to cast the deciding vote for Obamacare, and Democrats might still hold her seat). And to the extent that Republicans might try to block judges or cabinet appointees, the filibuster matters. But that is a two-way street (Lincoln Chafee might still be around had he not had to vote for parts of President Bush’s agenda), and in terms of advancing a progressive agenda, without the trifecta, the filibuster is largely superfluous.
So here’s the problem for Democrats: Republican trifectas are more likely, all other things being equal, than Democratic trifectas, at least in the near future. Let’s assume for the sake of argument that Democrats have a structural demographic edge in the presidency (I don’t agree, but let’s assume). Even the most rabid defenders of what we might call the Emerging Democratic Majority thesis concede that Republicans will still win the presidency if there is a recession, unpopular war, or other national upheaval.
Those contingencies happen with some regularity. So setting aside the fact that in the long run, presidential races sort out much the same way as do coin flips (the parties have each won the popular vote 20 times since the Republican Party was founded), let’s assume that in the short-to-medium term Democrats will win the presidency two-thirds of the time.
The House is another matter entirely. While it isn’t impossible for Democrats to retake the House (even in 2014), it is difficult. This is a subject worthy of a separate article, but given the current redistricting lines, and given how the Democrats’ coalition has sorted out into tightly packed geographic constituencies (urban liberals, minorities crammed into minority-majority districts), it makes a switch unlikely except in wave years.