The second week of NBC’s singing competition, “The Voice,” snagged more than 16 million viewers Monday from 8 to 10 p.m. — the time slot in which the network had averaged a measly 5.6 million viewers this season.

And at 10 p.m. — when NBC had been averaging fewer than 4 million viewers this season — the second episode of the network’s highly hyped “Smash” averaged 8 million.

Together, the two shows have handed NBC two consecutive Monday prime-time wins among the 18-to-49-year-old viewers it targets.

It’s the first time NBC has accomplished that with regularly scheduled programming in four years.

No Cain for ‘Dancing’

With Monday’s “The Voice” coming on strong in its first two episodes, the casting folks at ABC’s Monday/Tuesday show “Dancing With the Stars” are under a lot of pressure for the 14th edition, which debuts March 19.

“Dancing” is a competition series whose ratings rise or fall each edition based in large measure on the celebrity casting. So you can imagine how sorry ABC must be that former GOP presidential candidate Herman Cain has decided to decline the invitation to appear on “Dancing’s” new edition.

Polarizing political figures make for some of the best celebs on the BBC-produced program: They’re not only great at rallying blocs of viewers, but they also have this crack-cocaine-like effect on The Reporters Who Cover Television and/or Politics.

The network is still smiling over all the news coverage the show got in 2010 when Bristol Palin shimmied out of her gray business suit to “Mama Told Me Not to Come” and “You Can’t Hurry Love” while mother Sarah (a former GOP vice presidential candidate) led the pep squad in the audience.

And one year ago, reporters had their undies in a bunch over just the prospect of Christine “I’m Not a Witch” O’Donnell — the tea party candidate from Delaware who ran unsuccessfully for the Senate — being offered a spot on the show.

Like O’Donnell, Cain has declined to compete.

“He can’t dance in an eight-count. He can only dance in a nine-count,” an aide for former pizza-company big cheese Cain told a disappointed Atlanta Journal-Constitution on Tuesday — a ham-handed reference to Cain’s oft-derided 9-9-9 tax plan.

Lululemon case on TV

On Sunday, the Investigation Discovery channel will present its version of Jayna Murray’s murder in the season finale of “On the Case With Paula Zahn.”

Not quite a month ago, a Montgomery County judge sentenced Brittany Norwood to life in prison without parole for the savage killing of co-worker Murray last year in the Bethesda yoga shop Lululemon.

As The Post’s Paul Duggan reported: In an after-hours confrontation — apparently sparked by Norwood’s attempt to steal a pair of yoga pants — Norwood bludgeoned, choked and stabbed Murray, authorities said, using at least five weapons to inflict more than 330 separate wounds. Then Norwood gave herself a few minor wounds, bound her own hands and ankles in a restroom, and initially fooled detectives with an elaborate tale about a pair of masked intruders, according to authorities.

“ ‘On the Case,’ ” ID said, “is a shining example of ID’s core brand mission to investigate life’s mysteries through riveting storytelling” by unraveling “shocking investigations that have dominated headlines and intriguing original stories uncovered exclusively for ID’s audience.”

‘Machine’ test

The Discovery mothership network has just picked up a three-episode test for a new series called “Machines of Glory,” in which macho teams of machine operators compete to see who’s best at smashing fire hydrants, wrecking cars, torpedoing oil drums — as well as other exercises in large-scale destruction using excavators and backhoes.

And the winner of this competition gets “a cool $12,000 — because 10 grand wasn’t big enough,” host Johnny Littlefield brags of this paltry sum in the show’s promo reel.

It’s going to debut next month.

‘Key & Peele’ renewed

After telecasting just two episodes, Comedy Central has renewed its new sketch-comedy series “Key & Peele” for a 10-episode second season.

So far so good.

“Because ‘Key & Peele’ has been so immediately and universally well-received, I was worried if we didn’t give the show a quick pick-up, people might accuse me of being racist,” Comedy Central’s head of original programming, Kent Alterman, said in Tuesday’s announcement.

Because the two stars — Keegan-Michael Key and Jordan Peele — are black men, you see.

“We are honored, humbled and most importantly contractually obligated to deliver a second season to Comedy Central,” the two men said in their canned statement about the pickup, taking the high road.

The show launched two weeks ago behind “Tosh.0” and snared about 2 million viewers.