More than a quarter of Ted Cruz's original $38 million in super PAC firepower is sitting on the sidelines.

Toby Neugebauer is the wealthy donor behind Keep the Promise II, and sole source of the $10 million in the pro-Cruz super PAC's bank account. Neugebauer said during a telephone interview with the Washington Examiner on Monday that he plans to invest in the Texas senator's presidential campaign later in March, when the GOP primary moves into states where nominating delegates are awarded on a winner-take-all basis.

"I want to help Ted, but I want to be smart about it," Neugebauer said.

That's of no help to Cruz heading into Tuesday's spate of crucial GOP presidential primary contests in New England and across the South. The states that vote on Super Tuesday award delegates proportionally. These states, including Cruz's home state of Texas, have been a significant part of the senator's strategy for defeating front-runner Donald Trump — and rival Marco Rubio — and winning the 2016 nomination.

Trump, the New York celebrity businessman, is expected to roll to victory everywhere but Texas, where Cruz is favored. Rubio, the Florida senator, is competing with Cruz for second in most other states. But Neugebauer has said since seeding Keep the Promise II soon after Cruz launched his presidential campaign last year that conservatives who support the Texan should manage their resources to ensure that he has the financial support to compete in all stages of the race.

Neugebauer wasn't second-guessing his strategy on Monday, despite the uphill battle to capture the nomination that Cruz is likely to face coming out of Super Tuesday.

The Cruz campaign has been among the most prolific fundraisers of any on the Republican side in this presidential election cycle. The senator's operation had more cash in the bank than any other Republican candidate at the end of the third quarter fundraising period of 2015, and he raised around $20 million from October to December to close the year with more than $50 million raised.

Cruz's super PAC support has been more complicated. Rather than one independent political group taking charge of supporting the senator's campaign, his supporters chose to set up multiple entities that are separately controlled by the donors who fund them. The main collection of pro-Cruz super PACs include Keep the Promise, Keep the Promise I, Keep the Promise II and Keep the Promise III, although there are others.

The Keep the Promise super PACs were announced last year to much fanfare, in part because they were funded with more than $30 million between them. At the time, it was a major boost to Cruz's young campaign. But as of Super Tuesday, not all of that money has found its way into advertising and other political activities to boost Cruz's candidacy. Keep the Promise I, and Keep the Promise III, have been active on Cruz's behalf.

Keep the Promise II, as Neugebauer explained, is waiting for winner-take-all contests in Montana, Nebraska, New Jersey, Ohio, South Dakota, Florida, and Arizona, plus various U.S. territories.

The group's year-end report for 2015, filed with the Federal Election Commission and showing activity through Dec. 31, showed that none of the $10 million in its coffers was spent last year. According to FEC disclosures for super PACs that advertise for or against presidential candidates, the group has not spent anything yet this year, either.

Neugebauer said he has spent about $1 million on political activity to support Cruz, despite the expenditures not showing up on the FEC website's disclosure portal, including $300,000 in the last week.