The buyouts of TXU Corp., Clear Channel Communications Inc. and Harrah's Entertainment Inc. were three of the biggest of the 2005-'08 LBO bender. Today their debts are among the most onerous in the towering wall of speculative-grade loans and bonds that fall due from 2014 to 2017. TXU's and Clear Channel's loans constitute fully 18% of the total amount of leveraged loans set to mature in 2016.

The three also rank high on lists of potential casualties of the leveraged buyout wave. Here's how observers and debt investors size up their odds of survival and failure:

1. Energy Future Holdings Corp. Kohlberg Kravis Roberts & Co. LP, TPG Capital and Goldman Sachs Capital Partners' October 2007 buyout of the Dallas-based electric utility and power producer (formerly known as TXU) shattered records: It was the largest LBO in history, at $48 billion, and its $40 billion of debt was the most leverage ever put on an LBO. That debt now threatens to crush EFH.

Two years after the LBO, a steep drop in natural gas prices -- to which EFH's revenue is directly tied -- and a swooning Texas economy caused EFH's cash flows to plunge. Most experts expect natural gas prices to remain depressed.

EFH caught a break in April when lenders agreed to extend the due date on $15.3 billion of a key subsidiary's $22 billion of loans from 2014 to 2017. The company's limited ability to stream cash from its electric utility unit, Oncor, which is healthy, to the parent company gives it near-term breathing room.

But such moves will matter little if a prophecy of Moody's Investors Service credit analyst James Hempstead comes true -- that EFH will "run out of money by 2014" if it stays on its present course.

Vulture investors are circling the company. According to one EFH lender, distressed-debt players Centerbridge Capital Partners and Oaktree Capital Management LP refused to join other lenders in rescheduling loans to keep pressure on and force a restructuring. "They didn't extend because they want to get control," the lender says, adding: "The way I see it, [EFH's] problems are almost insurmountable."

The extended loans trade at around 72 cents on the dollar, a sign that other senior creditors agree.

2. Clear Channel Communications Inc. The San Antonio-based radio group's situation parallels that of EFH in key respects: The company's cash flow fell severely in 2009, the year after its $26 billion purchase by Bain Capital LLC and Thomas H. Lee Partners LP. Its bank debt trades in the 70s, a few points higher than EFH's. And it has a financially healthy subsidiary it can hit up for cash, Clear Channel Outdoor, a billboard business, of which it owns 89%.

But their plights diverge in important ways: Ebitda at Clear Channel's radio business, though still well below pre-LBO levels, appears to be on the mend. Moreover, notwithstanding its $20 billion debt burden, it doesn't confront the same risk of insolvency.

Clear Channel shaved debt at the parent company in 2009 when the billboard unit raised $2.5 billion of debt, which the parent raked off as a dividend and used to retire intracompany loans. Early this year, it refinanced nearly $2 billion in bank debt with junk bonds coming due in 2021.

It faces a big hurdle in 2016, when $12.3 billion of bank loans and unsecured notes expire. Remarks Fitch Ratings analyst Melissa Link: "Clear Channel obviously won't be able to repay the debt out of cash flow. So lenders will decide whether they want to keep the company going or if they want to extract whatever value they can" via a debt restructuring.

Says a lender: "We would be content to get par, which we think is a reasonable base case. On the other hand, if the company was unable to service its debt, we like these assets a lot."

3. Caesars Entertainment Corp. Even though Caesars (formerly Harrah's) carries the same shaky credit rating as EFH and Clear Channel, debt investors see it as an appealing turnaround candidate. Its 2015 loans trade in the mid-80s.

The Las Vegas-based casino and hotel operator's fortunes tanked along with Nevada's economy not long after Apollo Global Management LLC and TPG teamed up for a $31 billion buyout financed with $25.7 billion of new and existing debt.

As Caesars' cash flow ebbed, Apollo and TPG worked furiously to slash costs and reconfigure the balance sheet. They bought up swaths of debt themselves, pulled off a series of distressed-debt exchanges, coaxed lenders to stretch out maturities of more than $7 billion of secured debt and swapped some obligations for equity.

They trimmed $5 billion of debt. On Nov. 15, a year after a planned initial public offering was shelved, Caesars again filed papers to go public. Revenue and Ebitda remain in the dumps. "From a free cash flow perspective, after interest, they're probably burning through $350 million to $500 million a year. So they need to grow Ebitda," says a lender There's a fair chance that may happen, he adds.

"They have a lot of options for incremental Ebitda growth -- through further cost savings, acquisitions and joint ventures," he observes, citing as examples Caesars' 2010 purchase of Planet Hollywood Resort & Hotel and its gaming joint venture in Ohio, which has granted a limited number of gambling licenses.

The great hope is that Congress legalizes online gambling, a potential jackpot for stakeholders. "That's a very big factor in why people like this credit," the Caesars lender says.