Washington CNN —  

Sen. John Kerry, who sources say has been tapped by President Barack Obama to replace Hillary Clinton as secretary of state, will come to the post with a full plate of foreign policy crises, from the civil war in Syria, to the nuclear antics of North Korea, to a looming showdown with Iran over its nuclear program.

Anybody who follows Clinton would have some pretty big shoes to fill. Clinton was not just the most popular member of the president’s Cabinet for the past four years, she had celebrity status and respect almost everywhere she went around the world.

But as a member of the Senate Foreign Relations Committee for almost 30 years, the past four as chairman, Kerry himself is a highly respected figure on the world stage. While Obama is not close to a lot of world leaders, Kerry has deep relationships with many heads of state that he can draw on as the nation’s top diplomat. Sources close to the Massachusetts Democrat note that the increasing partisanship on Capitol Hill has disillusioned Kerry and he is ready to leave the Senate.

He is no stranger to diplomacy and has often traveled overseas on behalf of the Obama administration as a diplomatic troubleshooter and to mend frayed relationships. Kerry persuaded Afghan President Hamid Karzai to agree to an election runoff in 2009 and has traveled Pakistan after a series of incidents, including the raid that killed al Qaeda leader Osama bin Laden.

“There are very few people with greater experience over a longer period of time,” notes Nicholas Burns, a former career ambassador who has served every secretary of state since Warren Christopher, and was most recently undersecretary for political affairs under Condoleezza Rice.”He would be a very, very impressive choice.”

“You really need someone who is a renaissance person with a tremendous range of skill, both political and substantive, with a deep reservoir of knowledge” Burns said in an interview. “You need someone who can drill several layers deep on foreign policy issues.”

Like Obama, Kerry sees the benefit of reaching out to adversaries, like Iran and Syria, and give them a chance to negotiate. At one point, Kerry even spearheaded outreach efforts to Syrian President Bashar al-Assad before the administration turned on Assad over his crackdown on protesters. But he also has called for arming the opposition and for NATO airstrikes, which Obama’s administration has resisted.

The Middle East is sure to take up a good part of the secretary’s time. In addition to helping bring about a political transition in Syria, the United States also must manage the political chaos in Egypt and the rest of North Africa while trying to negotiate a nuclear deal with Iran and revive the Middle East peace process. Kerry is one of the well-traveled senators to the Middle East, has a good feel for the region and knows many of the players. Kerry insiders say a Secretary of State Kerry would want to play a big role shaping policy for in the Mideast and try to help solve some of intractable issues, including delving heavily into the peace process.

Kerry also has displayed a particular interest in climate change and energy, and sources say he is likely to give special emphasis to those issues. His wife, Teresa Heinz Kerry, has used some of her fortune to support environmental groups.

Kerry is viewed by those who know him as someone who is very hands-on with issues he cares about. He dives in and tries to understand the nuances, which often leads to a tendency to try to drive the issue. But part of being secretary of state involves managing an agency of more than 6,000 people and hundreds of diplomatic posts worldwide. A secretary must delegate authority and support leave the day-to-day diplomatic efforts to others, not try to be a day-to-day Middle East peace envoy or special representative for Afghanistan and Pakistan.

Much has been made of how Kerry’s relationship with the president could affect his effectiveness as secretary of state. While Susan Rice, who earlier this week withdrew her name for consideration, is considered to be one of President Obama’s closest confidantes. She shares, and perhaps even helped shape, his world view. Kerry is not seen as an Obama insider, but has been a presence at key moments in Obama’s rise. Kerry served with then-Senator Obama the Foreign Relations Committee and, as the presidential nominee in 2004, gave the young senator a platform that launched him onto the national stage when he asked him to speak at the Democratic National Convention. This election, Kerry also helped prep Obama for his debates with Mitt Romney and offered a strong argument of the administration’s foreign policy during his address at the convention in September.

Yet Kerry, like Clinton, does not have the close bond with the president, and his influence in forming and shaping U.S. foreign policy would be unclear. Kerry and Obama have their foreign policy differences – such as their positions on Syria. But in some ways, this could be an advantage. Even though there is not much daylight between the two men’s foreign policy visions, Kerry might be willing to challenge the president and present alternative viewpoints in a way that Susan Rice might not have.

Obama is considered a president who likes to drive foreign policy himself, and the White House plays a major role in both its conception and execution. If the president does choose Kerry, a lingering question remains whether he will empower his secretary of state to fashion areas of foreign policy on his behalf. Aaron David Miller, a Middle East expert with the Wilson Center, cites legendary former secretaries such as Henry Kissinger, James Baker and George Schultz as diplomats who were empowered to create the policies that their presidents then implemented.

“That is going to be the difference, I think, between John Kerry being a good secretary of state and … truly be a consequential, if not great secretary of state,” Miller said.

While the loss in the 2004 presidential election affected him for years, insiders say he has finally moved past it and is ready to serve under a president rather as president. Friends and colleagues say he would view the post as a chance to carve out an influential niche for himself in the administration and a place for himself in history.