Cruz's campaign has $13.8 million in the bank. (AP/LM Otero)

Sen. Ted Cruz (R-Tex.) reported more money in the bank than any other GOP presidential candidate as the last quarter ended, according to figures released by the Federal Election Commission Thursday.

Cruz's campaign raised $12.2 million last quarter, giving him a total of $26.5 million raised during the campaign so far. He  reported having  $13.8 million in cash on hand,  meaning he spent about 50 percent of what came in since his campaign started.  For the third quarter his spending rate is 58 percent.

The total raised by Cruz falls short of the $20.2 million reported this quarter by retired neurosurgeon Ben Carson. But the burn rate — the rate at which Cruz is spending money — is low compared to some of his competitors in the most recent reporting window: Florida Sen. Marco Rubio tore through 81 percent of the money he pulled in during the third quarter, a high percentage compared with an overall burn rate of about 40 percent since Rubio announced his candidacy.

Former Florida governor Jeb Bush had a burn rate of 86 percent during the third quarter, according to calculations by The Washington Post. Ben Carson spent 64 percent of his cash and Sen. Rand Paul (Ky.) spent $2 for every $1 donated,  according to Washington Post calculations.

[Read: Everything you need to know about the 2016 money race so far]

Cruz's campaign said it has so far spent $3.7 million to run the non-fundraising portion of its campaign operations, just 14 percent of the total.  The campaign meantime invested much of its resources back into high-tech fundraising efforts that used data analytics and a technique called "donor modeling."  The campaign reported spending $770,000 on web services and donor modeling in the third quarter. Of that total $750,372 was paid to Cambridge Analytica,  a firm that has developed state-of-the-art data analysis programs.

The result of such spending, said campaign manager Jeff Roe, is that the campaign has raised $18 million from a fundraising investment of about $8 million so far this year.

Cruz campaign officials said in an interview Wednesday that they have built a formidable two-pronged fundraising system designed to provide funds through a long campaign, an effort that draws support from both small-dollar donors and bundlers who bring in larger sums from associates and friends. The campaign has 219 bundlers who secured $9 million for Cruz as of Wednesday, Roe said. He added that the campaign has had 120,000 total donors through the quarter that ended June 30.

Developing donor lists is an extremely valuable asset to a campaign, noted Kenneth Gross, a former deputy counsel to the Federal Election Commission who advises campaigns — and the one the Cruz team has assembled is "a significant base of names," he said.

The campaign has begun experimenting with an array of fundraising techniques, including the use of text messages, an endeavor that has already proven lucrative thanks to a system of constant monitoring and adjustment of messages.

The operation pulled in $6.1 million online this quarter, spending $1.8 million for a return on investment of 328 percent, Roe said. It is also using sophisticated analytics to pull donations via a more traditional form of campaign solicitation: direct mail. The campaign has spent $1.1 million on mail, getting about $2.7 million in return.

It is unclear how much money has gone to Cruz super PACs since June 30, as the groups do not have to file with the FEC until the end of January.

Cruz often touts his fundraising totals on the campaign trail as evidence for the potential longevity of his campaign.

"In just over six months, we’ve raised 26.5 million from over 350,000 contributions," Cruz told a crowd in Fort Dodge, Iowa, Monday. The average contribution, he said, was $66.

"That’s the power of the grassroots. So I believe that our momentum is steadily growing," he said.

Another fundraising weapon: Cruz's wife Heidi, on leave from her job at Goldman Sachs, has become become the campaign's most prolific fundraiser, making 600 calls last quarter, she said. She told The Washington Post she aims to make 30 each day, but typically does about 20 to 25.

[Read: Heidi Cruz trying to close her biggest deal: Making her husband president]

She is looking for someone to give the maximum donation — and the perfect person to do so is conservative, middle class, a business owner who can afford to give to the limit and thinks it's a sacrifice.

"The calls that I’m making are to max out donors. Max out and super PAC," she said.

Matea Gold contributed to this report

This post has been updated