After fighting in Korea, Novak covered politics for the AP and The Wall Street Journal. In 1963, with his wife working in President Johnson's White House as a secretary, Novak teamed up with with Rowland Evans to start the "Evans-Novak Political Report, a daily syndicated column that Novak continued writing, after Evans' retirement, up through this last February.
Novak was a great reporter. That's undeniable. He also used his column to advance a conservative political agenda, which is, obviously, an old tradition that has made something of a comeback. But his advocacy journalism skirted ethical lines on multiple occasions, especially in his constant use of anonymous sources. In 1972, he quoted an unnamed Democratic Senator as saying presidential candidate George McGovern's platform was "amnesty, abortion, and legalization of pot." The catchier "amnesty, abortion, and acid" line caught on, though critics accused Novak of inventing the quote. Decades later, Novak claimed the quote was from Thomas Eagleton, McGovern's eventual running mate. Eagleton had just died, and thus couldn't confirm it.
And, more recently, Novak became famous for his revealing that Ambassador Joseph Wilson's wife Valerie Plame was a covert CIA operative, as part of a Bush White House attempt to smear a critic who'd correctly noted that they were inventing intelligence to justify a war against Iraq. Reporting that is generally understood to be a crime, but Novak was never prosecuted.
Novak's role, which he understood and embraced, was to act as a proxy for political attacks by conservative politicians. You leaked your smear to Novak, and he reported that "neutral" Republican sources said something nasty about McGovern or Joe Wilson or even Fred Thompson. He was also generally considered a mean old man and his brain tumor was diagnosed after he was hospitalized after he hit a pedestrian in his black corvette and kept driving, claiming to be unaware that he'd hit anything.