The New York Post is reporting that Tim Russert, longtime host of Meet the Press and Washington Bureau Chief for NBC News, has died suddenly of an apparent heart attack. Incredibly sad. He was only 58. More as we hear it.

UPDATE: The New York Times confirms Russert died this afternoon. WTOP has word that D.C. Fire and EMS responded to the NBC News Washington Bureau on Nebraska Ave. NW at 1:41 p.m. and found Russert in cardiac arrest. He was rushed to a nearby hospital in critical condition.

UPDATE II: Tom Brokaw came on the air around 3:40 p.m. and confirmed that Russert had died this afternoon at NBC’s D.C. offices. Russert had apparently been recording voiceovers for Meet the Press when he collapsed. Video below.

D.C. Mayor Adrian Fenty just released a statement: “On behalf of the residents of the District of Columbia, I want to extend our deepest condolences to the family of Tim Russert. He was a gifted journalist and a guide to the American political system for millions of television viewers. He was also a District resident and fixture in the nation’s capital for decades. We were privileged to have him be a part of our community, and will miss him greatly.”

Russert, who started in politics working for Senator Daniel Patrick Moynihan and Governor Mario Cuomo, was hired by NBC in 1984 and became Washington bureau chief in 1988. He had hosted Meet the Press since 1991, but his insightful political analysis reached even broader audiences during the 2000 election: When it was unclear how the election would turn, Russert used a dry erase board to explain the electoral college count. His use of a dry erase board was selected by TV Guide and TV Land as one of the 100 Most Memorable moments (#68) back in 2004.

Also in 2004, the Washington Post’s Howard Kurtz wrote a feature on him, “Tim Russert is the quintessential Washington insider, a man with tentacles deep into the political and media worlds, one of the few journalists in a puffed-up, preening profession who really matter.” This year, Time magazine named him one of the 100 most influential people.

NBC News recently revealed ambitious plans for covering the Democratic and Republican conventions–20 hours of live coverage each day; Russert would have provided coverage and analysis of the vice-presidential and presidential candidates’ acceptance speeches. Here’s how Russert predicted electoral maps for the 2008 election back in April, looking at possible Obama vs. McCain and Clinton vs. McCain matchups.

Russert, who regularly contributed to WTOP, had discussed the Obama’s campaign’s new website to fight myths about Obama this morning (MP3).

Jen Chung contributed to this post