Republican Sen. Ted Cruz has accused Texas Democratic Senate candidate Beto O'Rourke of taking money from a political action committee, in violation of O'Rourke's pledge not to take such donations.

O'Rourke has consistently outraised Cruz, including announcing a quarterly $10.4 million fundraising haul last month, despite the attention-grabbing vow to ban PAC money from his campaign coffers.

Cruz, who lost the 2016 Republican presidential nomination to Donald Trump, is seeking his second U.S. Senate term this November. O'Rourke is giving the conservative Cruz a high profile challenge even in a state that hasn't elected a Democrat to a statewide office since 1994.

A look at Cruz's claim that O'Rourke is "violating a pledge to reject PAC support," made this week in a campaign statement and on Twitter:

CRUZ CAMPAIGN: "Rep. Robert `Beto' O'Rourke travels all over Texas claiming that PACs are corrupt, and he's made his alleged rejection of PAC influence a cornerstone of his campaign ... But now we know that O'Rourke's actions have not matched his words."

THE FACTS: O'Rourke has not technically violated his campaign promise to eschew PAC money, but a PAC is encouraging members on its website to donate directly to the Texas Democrat.

O'Rourke, a U.S. Representative from El Paso, has promised not to take "a penny from PACs" in his bid for a U.S. Senate seat.

Cruz's campaign pointed out in a statement last week that O'Rourke has collected $172,000 from the J Street PAC, which supports Democratic candidates who favor a two-state solution to the conflict between Israel and the Palestinians. Cruz called on O'Rourke to return the cash.

O'Rourke's campaign finance reports do show $170,000 in donations tied to J Street PAC but the money came from individual donors, not the J Street PAC.

Here's how it works: J Street PAC lists O'Rourke as one of the candidates it supports in the 2018 midterm elections and offers a link on its website for anyone to donate to O'Rourke directly. The PAC also hosted an event to collect individual donations to put directly toward his campaign. The Federal Election Commission calls these "conduit contributions ," which means both the individual donor and the organization that gathered the money must be listed on campaign finance forms.

The FEC doesn't consider conduit contribution as PAC money, a spokeswoman for the agency confirmed. Neither do campaign finance experts, who say the donations are more transparent than PAC donations.

"No, it's not a PAC donation," said Victoria Farrar-Myers, an expert on campaign finance at Southern Methodist University in Dallas.

While O'Rourke hasn't broken his pledge, it is fair for Cruz to point out he's getting support from a PAC. The J Street PAC could only legally donate $5,000 to O'Rourke in each election cycle.

"I'm sure O'Rourke is more grateful for the ($170,000) in contributions than the $5,000," said Andrew Mayersohn, a researcher at the Center for Responsive Politics.

O'Rourke's campaign said he doesn't plan to return the money because individuals wrote the checks. The campaign has not accepted a direct donation from the J Street PAC since O'Rourke made the pledge.

Donors who make a conduit contribution must list their personal information, including name, employer and address. People who donate through a conduit contribution are still limited to the individual $2,700 cap per election. The process is less transparent with direct PAC donations, Mayersohn said. Typically, a person can donate up to $5,000 to a PAC. PACs can take the money they raise and donate up to $5,000 to a candidate, without listing individual donors, making the cash flow harder to trace.