How much money have Ted Cruz and Beto O'Rourke raised outside Texas? We don't know for sure.

Hey, Texplainer: Both U.S. Rep. Beto O’Rourke and U.S. Sen. Ted Cruz have raised tens of millions of dollars this election cycle. How much of each candidate's money comes from out-of-state donors?

In their race to represent Texas in the U.S. Senate, incumbent Republican Ted Cruz and Democratic challenger Beto O’Rourke have been at one another’s throats over who’s taking in more money from out-of-state donors.

Cruz has attacked O'Rourke for raising money in both New York and California, and even jokingly tweeted that Hollywood changed its famous sign to read, "Betowood."

“We've been told that Hollywood is afraid of being outdone by New York after last night's fundraiser, so now they're pulling out all the stops,” Cruz wrote earlier this month.

O’Rourke, meanwhile, has claimed his campaign is up against “outside groups” supporting Cruz that “could spend millions in Texas to try to tip the scales in Cruz’s favor.”

But the question of who’s getting more help from non-Texans is a tricky one.

Campaign finance reports show how much money is coming into a campaign and how that money is being spent. But federal law doesn't require candidates to disclose donors who give less than $200, meaning the sources of a big chunk of their contributions aren't reported.

“Contributions under $200 are thought to not have a big impact on elections. Those aren’t the large donors the FEC wants to track,” said Victoria Farrar-Myers, a senior fellow with Southern Methodist University’s Tower Center for Political Studies.

And because neither candidate has to disclose information about their small-dollar donors, it’s hard to paint a full picture of where Cruz's and O’Rourke’s money is coming from. An analysis by The Texas Tribune revealed that roughly 28 percent of the $15.6 million given to Cruz and 41 percent of the $23.6 million O’Rourke raised between January 2017 and the first six months of 2018 came from unreported sources.

“It’s difficult to make an apples-to-apples comparison,” said Dave Levinthal, a reporter at the Center for Public Integrity in Washington. “Especially with O’Rourke raising so much money from small-dollar donors, that definitely gives you a blind spot.”

But here’s what we do know: From the Jan. 1, 2017 through June 30, 2018, roughly 47 percent of Cruz's reportable donations from individuals have come from outside of Texas, compared to O’Rourke’s 33 percent, according to contribution data. However, this does not account for the $4.3 million Cruz's campaign has raised, nor the $9.7 million Beto's campaign has raised, that does not include a disclosure of the donor. (This also doesn’t include money raised for the race by super PACs, which are barred by law from coordinating with the campaigns.)

Though it’s hard to quantify who’s getting more support outside of Texas, here’s what each candidate’s campaign finance report will tell us: how much money they’ve raised, how much money has been spent, outstanding debt and how much cash each candidate has.

"Looking at itemized versus unitemized contributions for both candidates is a worthwhile comparison to use because it is apples to apples," Levinthal said. "Even though it won’t show the geography involved, it’ll show that Candidate A is getting 75 percent of his or her money from large dollar donors, while Candidate B is split. That’s a nice comparison that can be used to quantify grassroots support.”

The bottom line: Since neither Cruz nor O’Rourke has to report campaign donations under $200, you’re never going to get a clear answer as to which candidate is raising more money from donors outside of Texas.

Disclosure: Southern Methodist University has been a financial supporter of The Texas Tribune, a nonprofit, nonpartisan news organization that is funded in part by donations from members, foundations and corporate sponsors. Financial supporters play no role in the Tribune's journalism. Find a complete list of them here.