Red:
I agree the shutdown has the potential to do that, but I think it premature to make the "red" declaration you have. This shutdown, among shutdowns, is sui generis, but even so, it's just too soon to form a strong stance re: it's 2020 election impact. It is because many things, any number of which may override the shutdown in voters' 2020 presidential election "calculus," can happen between then and now.
For instance, if "the big one" strikes somewhere in CA, WA, OR while the government is shutdown, the shutdown could have a big impact. If the US finds itself in a war in, say, Venezuela, the shutdown won't matter much, and Trump would get the "war bump." (I mention that because of recent events in Venezuela and Russia's recently increased involvement, to put it mildly, there.) If the recession hits ahead of the election, Trump'll almost certainly, absent a war, be "toast."
Those are just some things within the realm of plausibility and that could indeed come about. There are plenty more that are equally and less "dramatic" that could coalesce to obviate the impact of the shutdown.