Newt Gingrich, pictured with wife, Callista Gingrich, checks many of the boxes that Donald Trump has said he is looking for in a vice president. (Larry Busacca/Getty Images)

Donald Trump will be the Republican presidential nominee this fall. He crossed the crucial 1,237-delegate threshold on Wednesday in North Dakota, taking what was a near-certainty and turning it into an absolute certainty.

With the question of whether Trump will win out of the way, we can move on to trying to figure out whom he will pick as his running mate. I did this once before, but so much has changed — for Trump and for the rest of the party relative to him — that it needed a total overhaul just a month later.

Below are my picks of the five people — Sen. Jeff Sessions (R-Ala.) would be sixth — most likely to wind up sharing a ticket with Trump. These rankings are based on conversations with Republicans, a study of Trump’s public comments about the various people in the VP mix and plain old intuition.

5. Joni Ernst. The senator from Iowa has a bright political future. Ernst emerged as a surprising star of the 2014 Senate class with a sterling résumé (military background, time spent in the state legislature, etc.) and a gift for communicating. She is well liked by many in the Republican Party and is seen as a fresh face — factors that should appeal to Trump. The question is whether Ernst wants to hitch her wagon — and her political future — to The Donald.

4. Bob Corker. The senator from Tennessee huddled with Trump last week in New York, a meeting that launched 1,000 stories about whether he was the pick. And Corker seems to be courting such speculation; his statement praising Trump in the immediate aftermath of the nominee’s foreign policy speech a few weeks back was very noticeable and not by accident.

With Donald Trump the clear front-runner in the Republican presidential primary, The Washington Post's Chris Cillizza says these are the five people the business mogul might pick as his running mate if he clinches the nomination. (Sarah Parnass/The Washington Post)

Corker is well respected in both parties in Washington as the rare politician who actually wants to get things done and who understands the sacrifices necessary to make that happen. Of the five people on this list, Corker would be the one who would make the Republican establishment happiest. But that might also be the reason, of course, that Trump won’t choose him.

3. Chris Christie. The New Jersey governor has sacrificed much to make this list. His decision to endorse Trump at a time when the Republican establishment was still focused on beating the real estate mogul turned Christie into persona non grata among lots of his old friends. But it also means that Christie has been by Trump’s side for longer than any other elected official. And his tough-guy personality and ability to win in a traditionally blue state probably appeal to Trump. Bridgegate continues to linger, and Christie’s numbers back home are atrocious, but does Trump really care?

2. Mary Fallin. The Oklahoma governor isn’t well known nationally but has the right sort of profile — conservative woman with executive experience — that Trump needs. She also spent some time in Congress, which should appeal to Trump, who has said that he wants someone who knows how Washington works. Trump made waves last month when he tweeted that former South Carolina lieutenant governor Andre Bauer’s recommendation that he pick Fallin as vice president was “great advice.”

1. Newt Gingrich. Gingrich checks many of the boxes that Trump has said he is looking for in a vice president: someone who knows Washington, understands policy and gets how Congress works. Plus, Gingrich was a relatively early supporter of Trump and has grown increasingly close to the real estate mogul , as detailed by National Review’s Eliana Johnson. ( Conservative news sites seem to love the idea, too .)

Gingrich’s weaknesses — ego, unfettered ambition, several high-profile marriages and divorces — would probably matter less to Trump than to other presidential nominees because they so closely mirror Trump’s own issues.