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So why would Mitt Romney want an endorsement from a self-promoting billionaire who loves to tell people "you're fired!"

Donald Trump is also more likely to turn voters off than turn them on to Romney.

Why would Romney want Trump's nod when it could be more likely to turn voters off than turn them on to Romney? A Fox News poll last month found that Americans were nearly three times as likely to say they'd be less apt rather than more apt to vote for a candidate Trump endorsed, 27 percent to 10 percent. Two-thirds said it would make no difference.

The most likely explanation is a Romney calculation that it's better to have Donald Trump on your side than against you.

The Donald has a penchant for needling his foes, whether it's President Obama or Rosie O'Donnell, and has a well-oiled PR machine at his disposal to dispense with his attacks.

Trump has also actively discussed - as recently as Monday with George Stephanopoulos - his possible bid as a third party candidate.

Either option could prove to be a thorn in Romney's side.

However, this assumes that The Donald won't change his mind - or his plans - at some point along the way. A real or perceived slight - or a need to boost ratings for his show - could be enough of an excuse for Trump to reengage the third party talk - or criticize the man he will soon be embracing.

Here is Stephanopoulos' interview with Trump from earlier this week: