Sen. Edward M. Kennedy of Massachusetts will be the Democratic nominee for president if he runs next year, and he will run, Sen. Henry M. Jackson (D-Wash.) predicted yesterday.

Jackson, himself a candidate in 1976, told reporters he still is supporting President Carter for the nomination, but he praised Kennedy lavishly for pursuing a course that "can't split the party."

"Kennedy will not get into it unless Carter takes himself out, or events take him out," Jackson declared. Jackson made it clear he expects one or the other to happen.

"The New Hampshire and Masschusetts primaries are going to be critical for Carter," Jackson said. "If he loses decisively in Massachusetts, that could be the Rubicon."

Kennedy, the senator continued, is "avoiding a course that says he's clearly running against the president. He wants to avoid forcing the president out of the primaries." And he added, "I think there is a strong feeling that a split in the party would not end with that office."

"Carter's problems create problems for the Democratic Party," he warned. A major split in the party could even endanger Democratic control of the Senate and perhaps the House, Jackson continued. "The [members] up for relection are worried. They are asking, what does it do to me."

Jackson all but stated that he expects Carter to lose the New Hampshire and Massachusetts primaries and that at that point Kennedy would become a candidate.

"The only thing that might cause him to come in ahead of schedule," Jackson said, "would be a Jerry Brown surge." Brown, the governor of California, is the one potential Democratic candidate that Jackson said he could not support.

Asked if he believes Carter deserves renomination, Jackson sidestepped, saying, "Well, I've done my best to help the guy. I worked my heart out on energy legislation ..."

Jackson termed Carter "the most convincing one-on-one person I've ever met." But he was critical of what Jackson called "his failure to understand the federal system," and caustic in references to Carter's appointment of Hamilton Jordan as White House chief of staff.

"The wisest move the president could have made would have been to name Bob Strauss chief of staff," Jackson declared. "He knows Congress and the federal system... He knows the Speaker and he returns phone calls."

The latter comments refer to the fact that Jordan met House Speaker Thomas P. (Tip) O'Neill Jr. for the first time last week and that Jordan often fails to return calls.

Jackson said Carter's Cabinet upheaval has "undone" the "definite plus" of his July 15 speech. The people in this home town of Everett, Wash., he said, "are bewildered. They are distressed by a lack of direction. They want to know who is running what."

The president's chances of renomination "are now very, very difficult," Jackson went on. "He has a very difficult situation. He can overcome it, but with what is past being prologue, it's tough. CAPTION: Picture, SEN. HENRY M. JACKSON . . . two 'primaries to be critical'