Presidential Wordsmith

If Karl Rove has been described as President Bush's brain, Mike Gerson has been the president's voice — a voice famously heard when Mr. Bush defined the enemy after Sept. 11 — "an Axis of evil arming to threaten the peace of the world."

CBS News correspondent Wyatt Andrews reports "axis of evil" was a line from Mike Gerson.

When the president proposed tough new testing in schools, he disarmed his critics by defining their opposition. It took six words — "the soft bigotry of low expectations."

"Soft bigotry" was also written by Mike Gerson.

"There are a few instances, a few moments in time, a few moments in history, where the words really count and matter," says Gerson about his contribution to the Bush administration.

According to colleagues, Gerson knows the president's thinking like no one else.

"We have a shared approach , a shared faith, a shared view of government," Gerson says.

Insiders say the President, in losing Gerson this week, is losing the aide with whom he bonded most, especially in areas of religion and faith. David Frum was on the team of writers working closely with Gerson.

"Mike famously made a point of introducing phrases from evangelical hymns, from religious language into the president's speeches," Frum says. "That was a language the president was very comfortable with."

It means Gerson's phrase, "axis of evil," was written with religious purpose.

Some people observe that there's a sense of morality in the use of the word "evil."

"It is a moral term, there's no question," says Gerson. "There's no other language that's adequate to describe the nature of the enemy under those circumstances."

Gerson is sometimes called "irreplaceable" because he gave the president so many unforgettable lines. The question is whether the president's ability to sound so eloquent at moments critical to the country goes away when Gerson does.

For the last year, however, Gerson has moved away from speechwriting and moved into policy areas, like Darfur.

"The emergence of Darfur as a major humanitarian crisis really shifted a lot of resources," Gerson says. "Me, the president, who was on this every day."

Some say Gerson is the conscience within the Bush White House, the one aide recalling the promise of compassionate conservatism, and then suggesting ways to act. Of all the big names who've quit the White House this year, it may be Mr. Bush misses Gerson the most.