Will Vegas help or hurt his approvals?
Probably help because (1) it distracts from Trump's Puerto Rico incompetence and utter failure, and (2) it's a national tragedy, his response wasn't horrible (at least so far, but you never know what he'll say about it tomorrow), and Americans tend to come together in tragedy.
I actually think it’ll sink the approvals. It’s obvious that he isn’t going to do anything about it and once all of the “thoughts and prayers” posts and tweets are posted, the media is going to start criticizing the GOP and Trump on their records. Remember that trump did sign an EO in his first week in office to ease restrictions for purchasing firearms for the mentally ill and the GOP has a bill similar to this on the floor now.
When have we seen any substantial media criticism, or any criticism that stuck, for Republicans after mass shootings before? Nothing will happen. Any criticism that is brought up will be dismissed for a) trying to politicize the issue, b) trying to restrict the rights of non-violent gun owners, or c) mental health or some other deflection.
I think Trump's ratings may go up a little bit but not by much. Nobody will pay attention to his speech today because he didn't say or do anything outrageous or uncharacteristic. If he's not advocating for any type of reform he will stay quiet and remain a non-factor. People aren't going to give him any credit if he's not doing anything so there won't be much improvement for his numbers.
