Financial disclosure reports released on Thursday offer a peek at the personal fortunes of lawmakers who could be potential running mates for Mitt Romney.  

Sens. Rob PortmanRob PortmanOPINION | They told us to abandon ObamaCare — then came the resistance Regulatory experts push Senate leaders for regulatory reform Conservative group to give GOP healthcare holdouts ‘Freedom Traitors Award’ MORE (R-Ohio), Marco RubioMarco RubioBush ethics lawyer: Congress must tell Trump not to fire Mueller The private alternative to the National Flood Insurance Program  Cruz offers bill to weaken labor board's power MORE (R-Fla.), John ThuneJohn ThuneSenate panel won’t vote on bill to boost ethanol Senate heads to new healthcare vote with no clear plan McCain absence adds to GOP agenda’s uncertainty MORE (R-S.D.) and Rep. Paul RyanPaul RyanGOP divided over care for transgender troops Want bipartisan health reform? Make the debate honest again Ex-CBO directors defend against GOP attacks on ObamaCare analysis MORE (R-Wis.) all released their yearly listing of assets and liabilities. Some of the VP contenders have lingering debts, while other are firmly ensconced in the millionaires’ club.

Portman's wealth climbed to at least $6.7 million in 2011, according to his financial disclosure form. That’s a 26 percent jump from 2010, when the former Office of Management and Budget Director reported $5.3 million for his minimum net worth. 

Portman’s liabilities dropped from at least $1 million in 2010 to at least $750,000 last year, which is partly responsible for the boost in his portfolio.

Combined with several hundreds of thousands of dollars in investment funds, Portman also has sizable holdings in real estate. He has a $1 million asset, for example, tied into an S corporation that has commercial rental property, buildings and vacant land in Cincinnati and Lebanon, Ohio, as well as in Erlanger, Ky.

Ryan’s worth is also in the seven figures. The House Budget Committee Chairman’s minimum net worth remained relatively the same from 2010 to 2011, dropping from $1.3 million to $1.2 million.

Among his assets, the Wisconsin Republican held at least $100,000 in gravel rights in Madill, Okla., as well as another $100,000 in a mining company in the same town. Ryan also reported one liability in 2011 — a mortgage on his personal residence in Janesville, Wis., for at least $250,000.

Under the STOCK Act, which passed earlier this year, lawmakers have to disclose mortgages on their personal residences for the first time. 

That might be why Rubio's minimum net worth decreased last year. His liabilities climbed to at least $550,000 in 2011, up from $200,000 in 2010.

Rubio reported a Chase home loan worth at least $250,000 and a U.S. Century Bank home equity loan valued at least $100,000 on his 2011 financial disclosure form; neither liability was on his 2010 report. He also has at least $100,000 in student loans with Sallie Mae.

Consequently, the Florida senator’s liabilities outweighed his assets in 2011, giving him a negative minimum net worth of negative $422,000.

Another vice presidential contender also might have found himself in the red because of the new requirement to disclose personal mortgages.

Sen. John Thune (R-S.D.) reported no liabilities in 2010. But Thune included two liabilities on his 2011 report — two refinanced mortgages that are worth least $100,000 each.

Thune's wealth declined from $170,000 in 2010 to negative $42,985 last year, according to financial disclosure reports. 

The reports do not give exact figures for lawmakers’ assets and liabilities but provide a value range for each. The Hill takes the bottom value of each item and subtracts the sum of a lawmaker’s liabilities from the sum of their assets to arrive at a conservative estimate for their net worth.

This story was updated at 6:28 p.m.

Rachel Leven contributed.