President Obama’s toughest policy battle will be gun control, according to the author David Maraniss who penned a book about the President’s life.

“The obvious becomes obvious only when it is obvious,” Maraniss wrote cryptically on Twitter. “Gun control, not fiscal cliff, is lasting test of Obama’s guts.”

“Then climate change…” he added.

Maraniss published his book ‘Barack Obama: The Story’ prior to the 2012 election – focusing primarily his upbringing. It is only the first of a series of books he plans to write about the President.

Maraniss was deeply impressed with Obama’s speech at the vigil in Newtown, Connecticut, Sunday night, comparing it to Lincoln’s Gettysburg address.

“There were so many levels to President Obama’s speech: philosophical, sorrowful determined universal, simple, beautiful,” he wrote. “People will long remember what Barack Obama said in Newtown … his Gettysburg address.”