Story highlights Obama has decided to nominate Sen. John Kerry to be secretary of state, Democrat says

A formal announcement could come as early as next week

U.N. Ambassador Susan Rice withdrew her name from consideration Thursday

President Obama has decided to nominate Sen. John Kerry to be the next secretary of state and could make a formal announcement as early as next week, a Democrat who spoke to Kerry told CNN Saturday.

The expected nomination follows U.N. Ambassador Susan Rice's decision to withdraw her name from consideration for the post. She dropped out of the running Thursday after weeks of criticism from Republicans about statements she made about the September 11, 2012, attack on the U.S. mission in Benghazi, Libya, which left four Americans dead, including Ambassador Chris Stevens.

If confirmed by the Senate, Kerry would replace current Secretary of State Hillary Clinton, who plans to leave her post within the administration.

Kerry, the senior senator from Massachusetts and the Democratic Party's 2004 presidential nominee, is noted for the experience, gravitas and relationship-building skills that could help him succeed as the United States' top diplomat.

Sen. John McCain, R-Arizona, recently jokingly referred to Kerry as "Mr. Secretary."

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In his current role as chairman of the Senate Foreign Relations Committee, Kerry has traveled the globe on behalf of the Obama administration to mend frayed relationships. Most notably he has traveled to Pakistan after a series of incidents, including the raid that killed al Qaeda leader Osama bin Laden, that had set relations back.

World travel is second nature to Kerry, 69. Born in Denver, he spent much of his childhood overseas, living in Berlin before going to a Swiss boarding school at age 11.

After graduating from Yale University in 1966, Kerry was deployed to Vietnam as a lieutenant in the U.S. Navy. Kerry served as a gunboat officer on the Mekong Delta, earning the Silver Star, the Bronze Star and three Purple Hearts.

Upon his return home in the early 1970s, Kerry gained public recognition as the head of the group Vietnam Veterans Against the War and for his anti-war testimony before the Senate Foreign Relations Committee.

In 1972, Kerry ran his first campaign, a losing effort for a congressional seat in Massachusetts. He eventually entered politics in 1982 as lieutenant governor under Gov. Michael Dukakis. Two years later, Kerry won the U.S. Senate seat he has held for five consecutive terms.

The Vietnam experience came back to haunt Kerry during the 2004 presidential election. A Republican-funded group called "Swift Boat Veterans for Truth" aired campaign ads accusing Kerry of lying to receive two of his five combat decorations and criticizing his anti-war activism.

Incumbent President George W. Bush won the Electoral College vote 292 to 252 and racked up 3 million more votes than Kerry.

After winning his fifth Senate race in 2008, Kerry took over the Senate Foreign Relations Committee the following January.

If nominated by the president and confirmed by his colleagues in the Senate, Kerry would leave Congress, and Deval Patrick, Massachusetts' Democratic governor, would appoint a replacement.

By state law, a special general election is required to take place 145 to 160 days after a vacancy occurs. So if Kerry were nominated, confirmed, and then stepped down on January 21 (Inauguration Day), the election would take place between June 14 and June 29, with primary elections being held six weeks earlier.

Whoever wins the special election would serve the final year and a half of Kerry's term and would then be able to run again for a full six-year term in office in the 2014 midterm elections.

Patrick says it's too soon to say whether he'll name a caretaker or appoint someone who would run in the special election. But a Democratic strategist in Massachusetts says Patrick is under pressure to avoid naming a caretaker, in hopes of preventing a divisive primary.

The strategist told CNN that both Rep. Ed Markey and Rep. Michael Capuano have already separately met with Patrick to ask for the appointment if Kerry's seat does open up.