There are four points worth mentioning about the explosive packages sent to liberal Democrats and their supporters. First, at a glance there hasn't been a trigger in any of the packages that would cause them to detonate when the packages were opened which indicates it wasn't an attempt to cause physical harm. Currently this would only serve one purpose and the benefit of sending them wouldn't be to thwart a persons political behavior by fear but secondly, a ploy to paint the opposing political party as the perpetrators. It's high unlikely that a person sending these package to a person of the same party would want them hurt.
Thirdly, most of the calls for violence has been coming from Democrats in congress such as Maxine Waters while there hasn't been the same call on the right. If this is the case and the sender is on the left it won't be the first time. In 2016 a church was burned down in Mississippi with writing on the side of the building that said "vote for Trump". It was later discovered that the person that did it was from the Church while a member and was trying to cast the blame on Trump supporters in order to help Hillary Clinton win the election.
Finally the fourth point is that of the profile of the person that would send it. It had to be someone of high stature within their political party that would have all of the addresses of all the targets that received the packages. It's unlikely that just anyone would have the address of John Brennan , former CIA director, as those are generally kept secret. But just recently someone had exposed the addresses of three Senators on the Senate Judiciary Committee of Sen. Mike Lee, Orrin G. Hatch, and Lindsey Grahm. And I would suspect that person's type would fit the profile of someone wanting to make republicans to take the blame for these packages and paint recently known perpetrators of violence such as Maxine Waters as victims themselves in order to help Democrats win the election. Judge Kavanaugh being a recent victim of a fraudulent viscous attack on his character just lead me to believe it was just another tactic by big liberal supporters that are trying to change the course of this election. I just don't believe an extreme conservative person to go through all of the effort to find all of the targets addresses and go through all of the trouble of making these bombs without one of them at least detonating and taking out a target. So for now I'm deeply skeptical about someone on the right being the cause of this chaos.