Strong case for it. Just look at the people who commit political assassinations and see what side of the spectrum they are on.
Please detail or cite any wide ranging study on the subject.
I'll start you off
The first Republican President, Lincoln, was killed by a anti-war lefty.
?!? Why wouldn't you describe him as a religious slavery enthusiast? Is it your position that he must be a "lefty" because he was against Lincoln? Is there any part of John Wilkes Booth's ideology that is remotely linkable to modern "lefty" thought? I'm not certain "Confederate" is really patternable on either party.
JFK was killed by a communist.
I'm glad someone finally knows who killed JFK
Charles Guiteau who killed Garfield had a long relationship with a utopian "free love" commune called the Oneida Community.
Guiteau also supported Garfield and was upset when Garfield didn't reward him with a patronage job following electoral victory. While he was obviously insane he at least believed he supported the Republican party.
Also, didn't he get kicked out of the Oneida's or was encourage to leave or something?
Czolgosz, who killed McKinley was a socialist.
Ummmm.....wrong. Anarchist. And from wiki: "However, it is worth noting that Czolgosz was a Republican. Like his father and brother, he voted in Republican primaries in Cleveland. During his attempts to get anarchist support, they turned him away because they thought he was a police spy. Czolgosz's interest in anarchism was greatly exaggerated in the press while his Republicanism rarely mentioned.[14] Such exaggeration appears to have been unnecessary, as Czolgosz's own words (including at his execution) and his devotion to notorious anarchist Emma Goldman and her beliefs make it clear that the impetus for his actions were to advance the anarchist cause. In addition, of course, it should be noted that McKinley was himself a Republican."
Zangara who almost killed Roosevelt was anti-capitalist.
It's unclear whether he was even trying to kill Roosevelt instead of the person he actually killed. Also, clearly insane.
Sirhan Sirhan who shot Robert Kennedy was a "Palestinian" angry with him for his support of Israel
Why does that make him Liberal?
Malcolm X was killed by Black Muslims
The stated motivation of which was criticism of Elijah Muhammad. That's a religious beef, not an overly political or "liberal" motivation.
What you are doing, however, is parroting an Ann Coulter line of thought that's not your own.
