The race for the 2016 Republican presidential nomination moved into a new phase over the last week as campaigns began to jockey behind the scenes to ensure delegates friendly to their candidate appear at the party's nominating convention later this summer.

Over the weekend in North Dakota, for example, allies of Texas Sen. Ted Cruz prevailed, claiming a majority of crucial unbound delegates -- delegates who are not bound to vote for any candidate during the first ballot at the convention. It's a playbook that anti-Donald Trump forces plan to repeat at upcoming state GOP conventions in hopes of denying the front-runner the necessary number of delegates required to secure the nomination.

But there's one wild scenario not many people are talking about: the vice presidential nomination.

As is the case for president, the delegates in Cleveland must also vote in their choice for vice president of the United States. Typically, the presumptive nominee makes a decision on his or her running mate before the party's convention, making the process of voting for the vice presidential nomination little more than a procedural check mark. In 2012, for example, Mitt Romney announced his running mate -- current House Speaker Paul Ryan (R-Wis.) -- several weeks before the convention.

If the three-man race between Trump, Cruz, and Ohio Gov. John Kasich truly drags into July and sets up a contested convention, as is looking likely, the GOP will have to select not just one but two wild-card candidates for the White House.

What makes the whole thing even more unpredictable is that, unlike the vote for the presidential nominee, delegates are completely unbound in voting for their candidates' running mate, as Republican National Committee Chair Reince Priebus noted on Monday.

"I do think it’s curious that people aren’t talking about [it], they’re talking about an open convention and the votes for the nominees, but people aren’t talking about the vote for VP. It could be quite amazing if that were to happen," Priebus told conservative radio host Hugh Hewitt.

"Everyone’s unbound. I mean, that’s the other thing. There’s no binding. There’s no first and second ballot binding. It’s just a free vote," he added.

Presumably, if the convention settled on a candidate squarely on the first or second ballot, the delegates would defer to their candidate's decision for a running mate. But if multiple ballots take place with no clear resolution, the backlash could spill over into the vote for the vice presidential nominee. One could for instance foresee a scenario in which Trump wins the nomination, but establishment forces push for a more palatable choice as their vice presidential nominee as a check against Trump's candidacy in the general election.