The first one is a good example. The second one is about a mentally ill British man whose "assassination attempt" never had any chance of success.
Should we count as political violence the plot to kill Barack Obama with a "death ray"? I think there's a distinction to be drawn between political violence and crazy people being crazy.
Interestingly, reading the pages you linked and dredging up the Death Ray link induced me to notice that (1) the previous shooting of a Congressperson was by a right-wing terrorist, and (2) that page about Obama recounts something like 6 very real plots to kill him mixed in among a bunch of variously mentally ill people being delusional. I think it's pretty clear which way the wind blows here.
There were also assassination attempts from the other side:
https://en.wikipedia.org/wiki/2017_Congressional_baseball_sh...
https://en.wikipedia.org/wiki/2016_Donald_Trump_Las_Vegas_ra...