He is not even an official candidate yet, but Joseph P. Kennedy III has a two-to-one lead over his closest would-be opponent in the race for the Massachusetts Fourth District Congressional seat, a poll released Thursday showed.

A poll of 408 Fourth District residents conducted by the University of Massachusetts Lowell and the Boston Herald showed Kennedy well ahead of leading Republican candidate Sean Bielat. Pundits said that the 30-point margin of Kennedy’s lead was larger than expected, but the poll’s results came as little surprise.

“I think it was sort of predictable,” Republican consultant Todd Domke said. “Maybe a little higher number than what might be expected, but he certainly was the presumed Democratic favorite. It’s a question of whether he’ll live up to the expectations.”

Kennedy emerged as the Democratic frontrunner in January when he announced that he would be leaving his post at the Middlesex Country District Attorney’s Office to explore a possible bid for the Congressional seat held by retiring Congressman Barney Frank ’61-’62.

Kennedy’s chief Democratic opponent, Boston City Councillor Michael P. Ross, disbanded his own exploratory committee two weeks ago, leaving Attleboro consultant Paul Heroux as Kennedy’s only prospective party rival.

Political analysts have suggested from the start that the 31-year-old Kennedy will garner support based on his family name. Kennedy is the grandson of former Attorney General and presidential candidate Robert F. Kennedy and the son of former Congressman Joseph P. Kennedy Jr.

The poll numbers released on Thursday show 73 percent of voters view the Kennedy family favorably. About half of polled voters said the family has the right amount of influence in the state, and roughly a third said they believe the Kennedys have too much sway.

“Here’s a young Kennedy without a scandal who seems nice and reasonable and intelligent, and they don’t care that he doesn’t have the usual qualifications and experiences,” Domke said. “They are willing to vote for the monarchy. The Kennedy family has a mythology with a lot of Democratic voters.”

Whether or not such name recognition and support will translate into votes over a Republican candidate come November is still uncertain, Domke said, but it will likely earn Kennedy his party’s nomination.

“What Kennedy has to do is run on something other than his name,” Democratic consultant Daniel Payne said. “He has to make sure he’s championing two or three issues.”

While Kennedy has quickly emerged as his party’s likely nominee, analysts said Bielat’s bid for his party’s nomination will be more difficult. Elizabeth Childs, a Brookline physician and former commissioner of the Massachusetts Department of Mental Health, has also launched a campaign to retake the longtime Democratic Congressional seat.

Bielat ran against Frank in 2010 and lost by 10.5 points. But the poll released Friday showed that 55 percent of voters in the district have not even heard of him.

“Last time he ran against Barney Frank he was a young, fresh face when voters wanted change—and he didn’t succeed,” Payne said. “This time, he’s not so young and he’s not so fresh.”

Kennedy, Bielat, Childs, and Heroux all hold Harvard graduate degrees.

The poll also asked candidates to rate the favorability of Sen. Scott Brown and Harvard Law School professor Elizabeth Warren, who are vying for a Massachusetts seat in the U.S. Senate. Fifty-three percent of voters said they have a favorable view of Brown, while only 36 said they saw Warren favorably. Twenty-nine percent of voters said they had never heard of Warren.

—Staff Writer Nicholas P. Fandos can be reached at nicholasfandos@college.harvard.edu.