Maybe we are looking at the Presidential election the wrong way.

Right now it seems certain one of three sitting US Senators will become President. When they give up their US Senate seat, how is their replacement chosen? Since all three are open borders maniacs, maybe it would be possible to put a pro-border Senator in their place? Which state would be more likely to send a pro-border Senator to DC, Arizona (McCain), Illinois (Obama), or New York (Clinton)?

How are replacement Senators chosen in these states?