Now that he has very likely secured the GOP presidential nomination, Donald Trump has turned his attention to a running mate. Trump brought Ben Carson on board to help him decide on a VP nominee, but don't count on it being Carson. The former Republican presidential candidate announced Thursday he was taking himself out of the running. When asked who Trump was considering, Carson reportedly mentioned a wide candidate pool that could include Democrats.

Carson told The Wall Street Journal, "We would consider people who are Americans and who put America first." If that includes a Democratic name, the chances of Trump bringing together an increasingly divided GOP party seem almost impossible.

In fact, who Trump ends up choosing will be important, considering Paul Ryan's remarks about needing the presumptive presidential nominee to unify the GOP. It's entirely possible that, once he gets to the Republican National Convention in July, the delegates won't accept his choice.

Trump's campaign manager Corey Lewandowski doesn't think that's likely, though. "I can’t imagine any scenario where the GOP nominee doesn’t have the opportunity to pick his own vice-presidential candidate," he said.

Regarding his decision to drop out as an option for vice president, Carson said: "I’m not interested in doing that for a number of reasons. I don’t want to be a distraction. I’m sure you remember how crazy the media was about me, I don’t want to be a distraction, it’s too important a time in our life."

In March, Trump's former rival endorsed him for president. "There’s two different Donald Trumps," he said at the time. "There’s the one you see on stage and then the one that’s very cerebral, sits there and considers things very carefully."