If the political vote is public, voters are exposed to blackmail or they may sell their vote. It’s a bad idea unfortunately.

https://xkcd.com/2030/

I appreciate that when you find a relevant xkcd, the explainxkcd page also has relevant information to the discussion:

https://www.explainxkcd.com/wiki/index.php?title=2030%3A_Voting_Software

When the reporter follows the interview up with a mention of blockchain technology, Megan and Cueball reflexively tell the reporter to avoid any voting system using the technology at all costs. Blockchain is a relatively new technology that is intended to solve some computer security issues by making it difficult to doctor old data. However, in the process of solving the old computer security issues, it has introduced new computer security issues that have not yet been ironed out; for instance, it doesn't solve input fraud issues, only data-doctoring fraud, so if a program caused the voting machine to record a vote for candidate B whenever a vote for candidate A was cast (such a program could be uploaded to the voting machines through USB, or through the internet which the voting machine must be connected to for blockchain), blockchain would not prevent it. Blockchain has also had a large number of high-profile scams, thefts, and implementations with critical security holes. Thus, Megan and Cueball may not trust this blockchain solution because of this history.

Blockchain is really great at preventing post-facto data changes. With blockchain you can somewhat guarantee that no one comes in after the election and changes the votes on the machines. (Unless they're handling the blockchain in a stupid fashion, for example without the distribution.) But you cannot prevent tampering with the machines themselves, such as making them record votes that didn't happen, or tampering the data before it's written to the blockchain.

Also, the security issues that Blockchain solves could also be solved via write-once memory, which would be more secure and more difficult to doctor.

Most computer security specialists are more worried about programs that randomly and/or deliberately misreport a vote, than people changing the votes after they're already recorded, so blockchain would solve an issue that most computer security specialists are less worried about, while causing new issues (the perpetual internet connection among them).