Correct syntax for chart overrides

I have a map with a popup link that opens a chart of related data. I want to move beyond the default axis labels and chart colors. I have working code for bar chart color overrides but I'm currently unable to get chart.overrides to work for axis labels.

code - https://github.com/eastmb/DeerHarvest/tree/gh-pages
result - https://eastmb.github.io/DeerHarvest/

**bar chart marks override (works):**

chart.override = {
marks: [{
properties: {
hover: {
fill: {
value: "#B80F0F"
}
},
update: {
fill: {
value: "#B80F8F"
}
}
}
}]
};

**attempted axis override code (not working):**

var overrides = {
"categoryAxis": {
"labelRotation": 70
}
};
chart.overrides = overrides;