One theory, which Alberto Gonzales would call "quaint", is that the lifeblood of the government is to be "of, by and for" the people.
Today things have changed, because we want change all the time, but it is debatable whether or not things have changed for the worse or for the better.
The U.S. Supreme Court has stated:
"taxes are the lifeblood of government"(Bull v. United States, 295 U.S. 247, 1935). The U.S. Department of Energy has what could be considered a different view:
"Oil is the lifeblood of America’s economy"(The Fleets & Terrorism Follow The Oil). I guess it all depends on whether or not the government is of, by, and for the people.
One thing is for sure, when the government is not of, by, and for the people the whole world gets turned upside down:
"taxes are the known instruments for bringing the many under the domination of the few"(James Madison). James Madison was the 4th President and was also called The Father of U.S. Constitution.
If oil is the lifeblood, it being a finite resource, and said to be peaking in 2014 (if it has not peaked already as some say) our nation needs a blood transfusion or we will die out economically.
The truth of the matter is that the earth environment with its oxygen, water, food, and protection is the lifeblood of every living thing and nation.
Green renewable blood is better than toxic oil blood because green is of by and for the people, in the sense that the people need new blood that will not run out, or destroy the environment along with humanity itself.