Standard & Poor's Ratings Services said today it lowered the ratings on certain public finance debt issues that have credit enhancement guaranteed by Federal National Mortgage Association (Fannie Mae) and Federal Home Loan Mortgage Corp. (Freddie Mac) to 'AA+/A-1+' from 'AAA/A-1+' following the downgrade of Fannie Mae and Freddie Mac to 'AA+/Negative/A-1+'. The outlook is negative. The rating on the affected debt issues is based on the rating on either Fannie Mae or Freddie Mac, which either