Continued from page 1

“It potentially is a headache for Obama because it does create a separate sphere of influence in the Democratic Party,” Mr. Shirley said. “They want the ability to move away from Obama if he becomes a millstone around their necks in the primaries.”

Mr. Sabato said, “The more the media and public focus on ‘16, the more it’s a distraction for Obama, who doesn’t want to be written off less than a year into his new term.”

Democratic National Committee spokesman Mo Elleithee, who was a spokesman for Mrs. Clinton’s 2008 presidential campaign, disagrees.

“I think we are all working toward the same goals,” Mr. Elleithee said. “I think there is a lot of energy behind the president’s agenda, whether it is passing comprehensive immigration reform with a path to citizenship, whether it is dealing with the budget and the looming showdown over that in the fall, or whether it is enrolling more people in health care.”

Mrs. Clinton has lived in the national spotlight since her husband, Bill Clinton, took over the White House in 1993.

In that first term, she ran a task force on health care, leading to a failed effort in Congress to overhaul the insurance system. Then she found herself in the middle of a political soap opera when Mr. Clinton’s sexual relationship with 22-year-old White House intern Monica Lewinsky was exposed.

After leaving the White House, Mrs. Clinton won a U.S. Senate seat in New York. She ran for the presidency in 2008 but lost the Democratic nomination to fellow Sen. Barack Obama.

In 2009, she agreed to serve as Mr. Obama’s secretary of state. She left the post this year just as questions were heating up over the Sept. 11 attack on a U.S. diplomatic post in Benghazi, Libya, that led to the deaths of the U.S. ambassador and three other Americans.

Mrs. Clinton has since hit the lecture circuit — her fee is $200,000 per speech — to speak out on social issues, immigration and health care. But she remains noncommittal on whether she will run.

With more than 1,170 days left before the 2016 election, polls show that Mrs. Clinton is the clear favorite to win the Democratic nomination.

History, though, might not be on her side. Mr. Shirley said Democrats have nominated the early front-runner in non-incumbent years just once since 1956, when Adlai Stevenson II was tapped as the party’s standard-bearer. It happened in 1984 with former Vice President Walter F. Mondale.