Is Syriza a Left-wing movement -- God forbid, maybe even a Socialist/Communist party in disguise -- as feared by unnamed prominent members of the European elite and as repeatedly declared by their paid hacks and propagandists in the Murdoch mainstream press?
Beyond any initial posturing by Syriza itself (for instance, as implied in its official name: Coalition of the Radical Left), presumably for the benefit of their lifelong activists, there's little reason to fear.
There are many ways to argue that (see James Petras, here, for one), but the chart above provides a clear reason: until the October 2009 election (won by the centre-left Panhellenic Socialist Movement/PASOK), the constituency of Syriza (313 thousand votes) was 1/7th that of centre-right New Democracy and 1/10th that of PASOK (5.2 million votes, combined).
After less than 3 years of Troika-imposed austerity, applied scrupulously by PASOK with ND support, Syriza's vote more than tripled (1 million votes), while the combined votes of PASOK and ND did not reach half their 2009 level (2 million votes): the PASOK/ND combined loss of 3.2 million votes reflected a gain for Syriza, other smaller parties (chiefly the Golden Dawn), and abstention (over 0.5 million voters did not vote).
The constituency of the Communist Party of Greece (KKE) has fluctuated around a narrow band (between 250 and 580 thousand votes), gaining little from the PASOK/ND loss. If there is any Left left in Greece, I'd search for it among those few.
Similar dynamics seem to apply to the June 2012 and January 2015 elections: quickly enough other smaller parties -- like a balloon -- started losing air; apparently, 1 Greek voter in 3 did not bother to vote.
The obvious interpretation of those results is that -- tired of austerity and disappointed by the corruption involving those two parties -- lifelong PASOK/ND supporters turned to the smaller parties less tainted by corruption or more critics of austerity, but perhaps not too distant ideologically.
If I had to find those lost PASOK (probably middle-class) voters, I'd look first among the supposedly "radical left" voters of Syriza (so much for the "Red under the bed" of popular imagination).
And, if I had to venture a guess, mine would be that those are highly volatile votes which could easily swing back to PASOK. But if ersatz Left floats your boat, then, by any means.
05-07-2015. Houses and Holes, from Macrobusiness, on the referendum: "It appears the Greek referendum that begins today is too close to call:" 43.0% No; 42.5% Yes. "81% favor Greece staying in the eurozone".