> how many senators have resigned or not seeking another term?

Not the US but a bunch of Aussie MPs have been resigning or plan to resign from the Liberal party. Liberal party was Turnbull's party and Downer's party when he was Foreign minister.

https://www.smh.com.au/politics/federal/fears-of-mass-exodus-liberals-brace-for-more-mps-to-quit-before-election-20190121-p50snk.html

I wonder if this is because of something that may come out eventually…