The last few days of drama over "repeal and replace" has shown the importance of individual senators, and the McCain operation has perhaps reminded people that death awaits us all.
As a morbid thought, suppose a Republican senator dies this month--how does that change political calculations? Or suppose it's a Democratic senator, they have some old ones too? Or to really go for broke, suppose there's an accident which takes out two or three senators?
[Note: this was written before announcement of Sen. McCain's cancer.]
[Added: note that Sen. Menendez (D-NJ) goes on trial later this year and Gov. Christie could appoint a successor.]