WASHINGTON — Conservative columnist and former CNN "Crossfire" co-host Robert Novak has died after a year-long battle with cancer, his family announced Tuesday. He was 78.

Novak died at home, just over a year after doctors diagnosed him with a malignant brain tumor in August 2008. He was a veteran columnist for the Chicago Sun-Times and a regular commentator for CNN for 25 years, beginning when the network launched in 1980.

For most of that time, he was a co-host of the political debate program "Crossfire." But he also hosted a show with his longtime column co-author, Rowland Evans, and appeared as a panelist on shows like "The Capital Gang" and on PBS' "The McLaughlin Group."

He was dubbed "The Prince of Darkness" by friends for his pessimistic persona, and he used the nickname as the title of his 2007 memoir.

Novak got his first newspaper job in 1948, when he was still in high school. He served in the Army during the Korean War before turning to the news business, eventually starting his column with Evans at the now-defunct New York Herald-Tribune in 1963.

In 2003, he found himself at the center of the scandal over the exposure of CIA agent Valerie Plame Wilson, when he published a column revealing her CIA status days after her husband challenged a key Bush administration justification for the invasion of Iraq. The scandal ultimately led to the conviction of Vice President Dick Cheney's chief of staff, Lewis "Scooter" Libby, on charges of perjury, obstruction of justice and lying to investigators probing the leak.

Novak cooperated with a special prosecutor and was not charged in the case.