ATLANTA --- The chairman of the state Transportation Board resigned Thursday to pursue a deeper relationship with the commissioner he oversees, further roiling the troubled Department of Transportation.

The move marked a stunning end to Mike Evans' five-year tenure just weeks after he fought off a challenge by House Speaker Glenn Richardson, R-Hiram. It sparked speculation that Transportation Commissioner Gena Abraham could step aside as soon as Monday, when the board has called a special meeting to handle the fallout.

Ms. Abraham has spent five months uncovering financial mismanagement at the department, which has overextended itself to contracts for transportation projects by as much as $1 billion.

Mr. Evans said he became friends with Ms. Abraham as they worked on the financial issues.

"Over the last month or so, we have developed a relationship that we both want to be more than just professional," he said.

Mr. Evans cast the key vote to make Ms. Abraham the commissioner last fall, then survived an attempt by Mr. Richardson to oust him earlier this year. Lawmakers who supported Mr. Evans with their vote in caucus elections lost offices and committee posts as punishment.

"There are those who suffered great losses in support of me," Mr. Evans said.