Donald Trump joked in last week's GOP debate that he was worried he couldn't pick Sen. Ted Cruz as his running mate because of questions about the Texas senator's eligibility.
It was a clever way of again raising what Team Cruz views as a ridiculous argument: the senator was born in Canada, yes, but his mother is from Delaware and an American citizen.
So, given the open war between the two candidates at the moment, a Trump-Cruz ticket appears unlikely.
But there is buzz in GOP circles about who might join a Trump-led ticket, which speaks volumes about the change in Republican thinking about the businessman's odds of winning the nomination. CNN's Nia Malika Henderson took us through some of the chatter:
"There was this idea of Trump and Kasich, Kasich being a balancer to Trump's outsider credits and Kasich being more establishment. I talked to John Weaver, who is one of Kasich's advisors; he said that was fantasy."
2) Cruz has a big-data operation -- but is it built on the right assumptions?
Big data is a big deal in today's politics, and the Cruz campaign is determined to set the 2016 standard: It has invested heavily, and believes that decision will pay big dividends when it comes to turning out voters in key contests.
The operation is built on a premise Cruz often talks about himself: that Republicans lose presidential races when they nominate more moderate candidates -- because, he argues, many conservative voters stay home.
Eliana Johnson of National Review walked us through the big questions about the Cruz data operation.
"Some of the assumptions from his campaign include the idea that 4 million conservative voters stay at home," said Johnson.
"He talks about the fact that 54 million evangelicals stayed home in 2012 and that he won 40% of the Hispanic vote during his Senate election in Texas in 2012. But that he could do that nationally is incredibly controversial among conservatives."
3) Tea party ally not officially on Team Cruz
Ted Cruz is a tea party favorite. So is Utah Sen. Mike Lee.
But Lee has not endorsed in the presidential campaign, and Jackie Kucinich of The Daily Beast walked us through the political calculations:
"Lee says it's because he's close to Marco Rubio and doesn't want to have to choose between his friends. But Utah insiders say Lee is acutely aware of how close he can get to Ted Cruz because of the shutdown. He had a huge drop in polls."
4) What a Trump win means for New Hampshire's first-in-the-nation primary status
Donald Trump has a big lead in New Hampshire -- and the prospect of a Trump victory has a lot of Granite State Republicans nervous.
It's not just a question of whether they support other candidates. It is a question of whether Trump winning would undermine their argument that New Hampshire should keep its first-in-the-nation primary status.
There is criticism every four years that Iowa and New Hampshire have too much influence; critics note those states are overwhelmingly white and also do not have the economic diversity of other states. The counter argument made by leaders in both states is that Iowa and New Hampshire have deep tradition of town halls and retail politics -- requiring presidential candidates to meet everyday voters and take their questions.
But Trump does things his way -- and Matt Viser of The Boston Globe says some New Hampshire Republicans are worried their state could pay a price.
"The party is a little bit on edge up there because there's already efforts within the RNC to take away the first-in-the-nation status," said Viser. "Reince [Preibus] said there are no sacred cows going forward in 2020."
5) One "Amigo" is in the Bush camp -- and another is being courted
Sen. Lindsey Graham endorsed Jeb Bush this past week, calling him best-prepared among the Republican candidates to be commander in chief.
Graham's own presidential campaign didn't get very far, but Bush is hoping his endorsement helps in the senator's home state of South Carolina. And now, the former Florida governor is trying to enlist Graham's help in winning another high profile endorsement: that of Arizona Republican Sen. John McCain.
McCain, of course, was the 2008 Republican presidential nominee, and traveled often with Graham and then-Sen. Joseph Lieberman of Connecticut. "Three Amigos" was their self-styled nickname.
Team Bush wants a McCain endorsement for two big reasons: to quiet talk that the Bush campaign is no longer viable, and to echo Graham's case that Sen. Marco Rubio isn't ready to be President.
But GOP sources familiar with the conversations describe McCain as hesitant to get involved in the primary campaign. He has a complicated history with the Bush family; McCain was a rival of George W. Bush in the 2000 campaign and then was a vocal critic of the Bush administration's handling of the Iraq war. He is also up for re-election this year in Arizona, and one friend aware of the Bush campaign lobbying effort predicted McCain would stay neutral.