The prosecutors have also been looking at a string of personal and campaign loans issued to the Clintons by several small Arkansas banks during the 1980's and 1990's.
First Commercial, the biggest Arkansas bank, is on the block because it was expected to have difficulty expanding beyond its relatively narrow market.
Investigators said about $12,000 from Madison Guaranty had been deposited in Mr. Clinton's account at another Arkansas bank for the 1984 gubernatorial campaign.
Investigators asked the Clintons about a $5,000 personal loan Mr. Clinton took out from an Arkansas bank in 1979.
Financial disclosure forms show that for his initial campaign he borrowed almost $450,000 in short-term, high-interest loans from eight Arkansas banks.
The Treasury's consolidation of regulatory authority would take the Arkansas bank and hundreds of other banks out from under the Fed's oversight.
He said he owes at least $348,000 in interest and principal to the two Arkansas banks.
His campaign now owes an Arkansas bank more than $2.7 million.
First Commercial is the largest Arkansas bank and would give Regions a strong foothold in the state.
The trial centers on the 1990 campaign's relationship to the Perry County Bank, a tiny Arkansas bank that held the campaign's deposits.