VETERAN news star SAM DONALDSON is reeling from a tragic divorce secret that paved the way to his recent headline-making DUI bust, say sources.

Months before he was pulled over by Delaware police, Jan – his wife of 29 years – walked out on the blustery, 78-year-old newsman. As The ENQUIRER recently reported, Donaldson was already shattered by his declining career, and friends fear he’s in the early stages of dementia.

“Sam and Jan separated quietly a few months ago, and now he’s scared to death that she’s going to file for divorce any day now,” revealed a close source.

Distraught over his mari­tal problems and his health, the former ABC White House correspondent hit the bottle hard to ease his loneliness, say insiders.

“He loves Jan dearly,” di­vulged a close source. “Sam really thought they’d be mar­ried for the rest of their lives.”

After Donaldson was diag­nosed with melanoma of the lymph nodes in 1995, Jan, 57, lovingly cared for him.

“She was his rock, and Sam is forever in his wife’s debt,” said the source. “But as time went on, he grew more belligerent and could get angry when he drank his whiskey. When she left, it was a terrible blow. He was so ashamed he couldn’t even admit to some friends that Jan had fled.

“The shock of the separation drove him to drink more and more.”

Donaldson was driving alone on Dec. 1 when Lewes, Del., officers stopped him. He was ar­rested on a misdemeanor charge of driving under the influence and failure to remain within a single lane. The case has not yet been scheduled for trial.

Friends now worry he could fall into a deep depression.

Said the source: “The biggest fear is Sam will continue to rely on the bottle.”