Sen. Ted Kennedy had a good night sleep and his condition appeared to be improving Sunday as his friends, family and colleagues congregated around him after two apparent seizures sent him to a Boston hospital.

Kennedy spokesman Stephanie Cutter said Kennedy was awake, alert and spending time with his family in between treatments at Massachusetts General Hospital to determine the nature of the episodes that sent him there a day earlier.

• On the Scene: FOX News' Laura Ingle Blogs From the Hospital

Kennedy, 76, did not suffer a stroke and "is not in any immediate danger," said Dr. Larry Ronan, the senator's primary care physician, said Saturday. He was "conscious, talking, joking with family," according to a spokeswoman.

Kennedy was sedated for a brief period of time Saturday upon arriving at the hospital, and this was done as a standard, precautionary procedure. Upon waking, he joked with his family and watched both games of a Red Sox double-header. Kennedy not only ordered out for Legal Seafood Clam Chowder but, actually ate some himself at the hospital, sources familiar with the situation told FOX News.

"Over the next couple of days, Senator Kennedy will undergo further evaluation to determine the cause of the seizure, and a course of treatment will be determined at that time," Ronan said.

Kennedy, the liberal anchor of the U.S. Senate and remaining patriarch of the storied Kennedy family, suffered one seizure in the morning, and then another en route to Massachusetts General Hospital.

Kennedy was flown to the Boston hospital an hour after first being admitted to the emergency room at Cape Cod Hospital at about 9 a.m., hospital spokesman David Reilly told FOXNews.com. He was joined at the hospital by wife Vicki, niece Caroline, nephew Joe, his sons Teddy Junior, Patrick, and daughter Kara.

"He is undergoing a battery of tests at Massachusetts General Hospital to determine the cause of the seizure," Kennedy's Senate office said in a statement. "Senator Kennedy is resting comfortably, and it is unlikely we will know anything more for the next 48 hours."

Sources said one of the reasons the family is waiting 48 hours for test results is because at least one of the tests is related to enzyme analysis. Cutter would neither confirm nor deny the test.

As word of his condition spread, well-wishers poured out to express their concern and hopes for a swift recovery.

"There'll be some tests I guess on Monday, but he seems to be doing pretty well. And we just hope for the very best for him and are confident he'll be fine," said Sen. Chris Dodd, D-Conn., said Sunday.

Kennedy was also visited at the hospital by Senate colleague John Kerry, D-Mass. The hospital is highly regarded and Kennedy has received treatment there before for other medical problems.

"Ted Kennedy is beloved and respected on both sides of the aisle in the Senate in which he's been a giant for close to half a century, a legend in Massachusetts," Kerry said in a statement. "We know that everyone in Massachusetts and people throughout the nation pray for a full and speedy recovery for a man whose life's work has touched millions upon millions of lives."

According to an article in the Cape Cod Times, Kennedy had first fallen ill at the Kennedy compound in Hyannisport. Hyannis Fire Lt. Bill Rex told The Associated Press that a 911 call came in from the compound at 8:19 a.m.

Kennedy is the second most-senior member of the Senate. The Democratic senator was first elected in 1962, to fill out his brother John F. Kennedy's term.

Kennedy also is one of Democratic presidential candidate Barack Obama's biggest supporters, and has kept a hectic schedule campaigning for him — a factor one source said may have created some extra stress for Kennedy.

"Obviously my thoughts and prayers are with Teddy," Obama said Saturday in Oregon, where he was campaigning. "He is one of my favorite people and so hopefully he is going to be okay."

On Sunday, the Obama campaign said the candidate spoke to Kennedy from his hospital bed, and the senator sounded energetic. Aides said Obama described him as "the same old Ted."

The other presidential candidates also expressed their concern.

In October, Kennedy had surgery to repair a nearly complete blockage in a major neck artery. The discovery was made during a routine examination of a decades-old back injury.

The hour-long procedure on his left carotid artery — a main supplier of blood to the face and brain — was performed at Massachusetts General. This type of operation is performed on more than 180,000 people a year to prevent a stroke.

The doctor who operated on Kennedy said at the time that surgery is reserved for those with more than 70 percent blockage, and Kennedy had "a very high-grade blockage."

Kennedy is the lone surviving son in a famed political family. His eldest brother, Joseph Kennedy, was killed in a World War II airplane crash. President Kennedy was assassinated in 1963, and their brother Robert Kennedy, attorney general in the Kennedy administration, was assassinated in 1968.

Considered a liberal lion in the Senate, Edward Kennedy was re-elected in 2006. His current term ends in 2013. The senator made a failed run for the presidency in 1980.

Despite his health problems, Kennedy maintains an aggressive schedule on Capitol Hill.

Colleagues and former aides described him as an institution, one known as the scourge of conservatives but also willing to get behind bipartisan legislation.

“He has a charm and I don't know anybody that equals it," said former colleague and Sen. Dennis DeConcini.

“No one works harder, cares more, is willing to fight to the last second for the causes he believes in — even when there’s no chance of winning,” strategist and former Kennedy campaign staffer Susan Estrich told FOX News.

Click here to read about the presidential candidates' reaction to Kennedy's hospitalization.

FOX News' Major Garrett, Trish Turner, Judson Berger and Bonney Kapp and The Associated Press contributed to this report.