Obama as warrior and healer

It is not an easy job, being US president. There are so many tasks, so many facets, so many duties and desires. It is not always easy to pivot from one to another.

Having stood in the Rose Garden as the fierce champion of a cause that divides America, he must now attempt to find words that comfort his country and bring his people together.

The president's different messages are united by what they seek to deal with - violent crime and the murder of innocents.

President Obama will soon be in Boston speaking at an interfaith service for those killed in the Boston bombings.

His task is to unite and reassure a country that has every right to be nervous after the bomb attacks. He will try to do this by praising the heroism that was on display on Monday, praise it as the essence of America, resilient and compassionate.

Legacy as president

He can be good at this. But he is better when the cadence of his words reaches the climax of a call to political action.

This is a president for whom it is not enough to embody his country. He wants to change it. After the murders at Sandy Hook school he wholeheartedly embraced the cause of greater gun control. The latest vote by the Senate suggests that it is doomed.

They voted down extending background checks to people who buy from unlicensed dealers, at gun shows and online. In fact, what they rejected was a watered-down bipartisan compromise.

Mr Obama spoke in some of harshest, strongest terms I can ever recall him using. He said the pro-gun lobby had "lied" about the bill, that the vote was a "shameful" day for Washington.

He strongly implied many Republicans and some Democrats were cowards, putting fear for their jobs before doing the right thing, saying they had "caved in".

He promised that this would not be the end.

I'm still uncertain what his strategy is, although he certainly pointed clearly to next year's mid-term elections:

"You need to let your representatives in Congress know that you are disappointed, and that if they don't act this time, you will remember come election time."

I've little doubt he will speak with moving passion in Boston. But he is at his best when his words seek to leave the world a different place.

Combating terrorism is a deadly serious duty for any president, but not one of the reasons Mr Obama wanted high office in the first place.

His fighting words in the Rose Garden will not be the last we hear of a campaign that Mr Obama has put at the heart of his presidency and his legacy.