Throw in D66's result and the Pirate Party's meager 0.3%, however (but not 50 Plus - thank you for your earlier feedback), and you get to 47% of the vote. That's a more flattering comparison, since D66 did much better now than in 2003 and 2006. In fact, 47% for the 'broader center-left', if you will, is the second best score in post-war history, after 1998 (49%), and on a par with 1981 (47%).
Can D66 really be considered part of the "broader centre-left" any more, though? They seem to have embraced a lot of right-wing economic ideas, and I think a centre-left liberal party ought to be prepared to work with the SP. The impression I get is that they've moved into the right-wing liberal space vacated by the VVD as the VVD becomes the main right-wing party; I don't think the VVD can really be considered "liberal" in a British English sense any more, whatever their European affiliation.