Update 11:10 p.m. ET:
Vice President Joe Biden, a former senator himself, condemned the GOP senators' letter in a strongly worded press release late Monday, calling it "beneath the dignity of an institution I revere."
State lawmakers face a major deadline by the end of the week, as the 2015 legislative session heads into its final stretch.
Friday, March 13 is crossover day. That is when bills must pass in one chamber in order to stand a chance of getting approved in the other.
The Georgia House has passed a bill aimed at producing millions of dollars for the state's transportation needs after a full day of discussion about last-minute changes.
The bill passed on Thursday 123 votes to 46.