Because of Election Night tomorrow, this week’s “election” on The Voice takes place tonight only, with all 20 remaining contestants performing live, and hoping to move on, thanks to viewer vote, to the Top 12. So far, this has been a year with a strong array of impressive talent, and some of them are bound to shine, as well as falter, in the glare of the live TV spotlight. But also, so far, the two new judges, Miley Cyrus and Alicia Keys, have grabbed and used the spotlight shrewdly and very, very effectively.