I'm speculating here, but my impression is that condemning a politician on the basis of whom they've shook hands with is much more commonly a conservative behavior, and that it may be due to a moral value of purity, such that it's unacceptable for a politician to associate with sufficiently undesirable figures and display anything that might appear to be approval, regardless of whether or not they take actions favoring that figure.
Really? The only thing my brain pattern matched to "embarrassing handshake, political" was the Rumsfeld-Hussein handshake. Google for "hussein handshake" for me claims 15+ million hits, and the front page is all Rumsfeld. If you consider politically-charged-body-language in general, I can recall the US right-wing being upset that Obama bowed to foreign leaders and the US left-wing being upset that Bush Jr. held hands with the Saudi crown prince, but I never had the impression that even this broader category of complaint was common fr...
Another one for the memory-is-really-unreliable file. Some researchers at UC Irvine (one of them is Elizabeth Loftus, whose name I've seen attached to other fake-memory studies) asked about 5000 subjects about their recollection of four political events. One of the political events never actually happened. About half the subjects said they remembered the fake event. Subjects were more likely to pseudo-remember events congruent with their political preferences (e.g., Bush or Obama doing something embarrassing).
Link to papers.ssrn.com (paper is freely downloadable).
The subjects were recruited from the readership of Slate, which unsurprisingly means they aren't a very representative sample of the US population (never mind the rest of the world). In particular, about 5% identified as conservative and about 60% as progressive.
Each real event was remembered by 90-98% of subjects. Self-identified conservatives remembered the real events a little less well. Self-identified progressives were much more likely to "remember" a fake event in which G W Bush took a vacation in Texas while Hurricane Katrina was devastating New Orleans. Self-identified conservatives were somewhat more likely to "remember" a fake event in which Barack Obama shook the hand of Mahmoud Ahmedinejad.
About half of the subjects who "remembered" fake events were unable to identify the fake event correctly when they were told that one of the events in the study was fake.