If this were implemented, for probably 90% of votes that he casts, we would see very low turnouts with voters coming from two groups: special interests--the small group of citizens who are deeply affected by the outcome of the vote and thus find it worthwhile to vote; and political junkies who get satisfaction out of voting on every issue, but who probably don't actually have time to really be informed about every single bill, especially as they evolve.
Implementation would also be extremely challenging. How do you ensure that Oregon residents (and which residents?--those who are eligible to vote? Those who are registered to vote? All, even children, felons, etc?) can vote once, and all others cannot vote? How do you handle people whose credentials for voting (whatever they may be) are compromised? What happens when a bill is amended--do people who have already voted on it have their votes stand by default? Are they able to change them? If they're able to change them, is that at the expense of anonymity? Do you actually have anonymity anyway? How does the Senator vote if someone DoS's the voting system? And obviously if there are any security vulnerabilities in the system, lots of problems could arise. These are very hard problems; there's been quite a bit of research into evoting, yet it is still very much an unsolved problem. If someone wins on a direct democracy platform, these problems will become very apparently very fast.
Senators have access to a list of registered voters, which could help curb fraud.