By Keith Laing - 07/14/12 07:27 PM EDT
Polls show support for the transportation tax proposal has been slipping in recent weeks.
If the transportation tax is approved by all 12 regions of Georgia that are scheduled to hold votes on it, supporters have said it will generate $18 billion for road and transit projects in the state.
A list of projects the money would be used for was approved by local officials after months of contentious debate.
-This post was updated at 4:41 p.m. to clarify that Sen. Chambliss has not formally endorsed the transportation tax.