The State of the Union address is always a momentous occasion, but this evening, it’s a little more meaningful than most. Not only is our Head of State speaking before an American public that disapproves of his job performance by nearly a 2-to-1 ratio, but many in the audience will be envisioning themselves in his position.

The sheer number of lawmakers reaching for that chance distinguishes the crowd assembling for President George W. Bush on Tuesday night from any other State of the Union address in recent memory. And it’s already showing.

According to the Washington Post, some of the White House aspirants are unwilling to let Bush have the first word and then gamely react. The candidates are already in motion, playing off his themes (both recurring and expected) in their own way.

Democratic Sen. Hillary Rodham Clinton of New York spoke of health care, the Iraq war and more on a day packed with four television interviews, a news conference, a Webcast and an appearance before the Senate Armed Services Committee where she appealed for better equipment and security for troops.

“The Humvees are turning into death traps,” complained Clinton, who announced the formation of her presidential exploratory committee last weekend.

Sen. John McCain of Arizona commanded attention in that hearing room, too. The 2008 GOP presidential prospect, who has been a supporter of the war throughout and backs Bush’s proposed troop increase in Iraq, explored the consequences of pulling out.

“It took us a long time to recover from losing a war,” he said, in a reference to Vietnam, where he spent five years as a prisoner.

Democratic Sen. Joe Biden of Delaware led a Foreign Relations Committee hearing rich with presidential prospects, including himself.

Illinois Sen. Barack Obama arranged a last word of sorts, a late-night TV interview after Bush’s speech and the formal Democratic response to it. He announced his guest for the speech, celebrated South Side Chicago schoolteacher Rana Khan.

Even non-Washington lawmakers joined in:

• New Mexico Gov. Bill Richardson, a former House member and energy secretary who announced his Democratic presidential candidacy last week, took part in a telephone briefing to discuss climate change and energy issues.
• Democratic candidate Tom Vilsack, former Iowa governor, didn’t wait to hear Bush’s speech before criticizing it in a “pre-buttal.”
• Former Vice President Al Gore, who has not ruled out running again, saw his film on global warming earn two Oscar nominations.

The speech will be the first in years with so many serious contenders in the House chamber, but that’s not the only unusual thing about it - the dramatic introduction to the event will make history.

The opening words of the sergeant-at-arms, as he ushers Bush inside the chamber, will be amended to account for California Rep. Nancy Pelosi’s historic rise as the first woman to lead the House: “Madam Speaker, the president of the United States!”

Aside from that piece of history and their own aspirations, the State of the Union will be old hat for some of the candidates. Clinton sat through eight of them as First Lady, two shadowed by the Monica Lewinsky scandal that led to her husband’s impeachment.

Not since 1976 have there been more senators running than this year’s six, said Senate historian Donald Ritchie. Democrats Clinton, Obama, Biden and Chris Dodd of Connecticut, and Republicans McCain and Sam Brownback of Kansas have all thrown their hats in the ring.

Senator John Kerry of Massachusetts, the Democrats’ nominee in 2004, may still declare his candidacy. His running mate, former Senator John Edwards of North Carolina, has already joined the crowded field.