From the podium to the House floor and the gallery above, the heartbreak of the Jan. 8 Tucson shootings looms over the packed chamber Tuesday evening when President Barack Obama delivers the annual State of the Union address.

At the rostrum, Obama is expected to speak in healing tones to a nation and a Congress still grappling with what role, if any, fiery political rhetoric played in sparking the mad attack not three weeks earlier that left six people dead, Rep. Gabrielle Giffords with a bullet wound to the head, and 12 others injured.

Behind him: the new Republican speaker of the House, John Boehner, sworn into his position as second in line to the presidency less than a week before the shootings.

Gazing down from the gallery: the faces of the tragedy.

John and Roxanna Green, the parents of 11-year-old Dallas and the late Christina Taylor, the 9-year-old girl born on 9/11 and killed in the Tucson attack.

Daniel Hernandez, the Giffords intern who helped clear the wounded congresswoman’s airway and held her until medics arrived.

Giffords’ Arizona medical team — trauma surgeons Peter Rhee and Randall Friese, neurosurgeon Michael Lemole and nurse Tracy Culbert.

Below them in the audience, Republican and Democratic lawmakers are making a show of unity. Carefully courting each other like prom dates, many will sit elbow-to-elbow rather than the traditional party-by-party. Black and white ribbons, signifying the deaths of the Tucson victims and the hopes of the survivors, were to be pinned to lapels across the chamber.

The proximity of lawmakers to the president and to each other is often seen as a measure of power, goodwill and grudges. So, mixing it up, participants hope, might be a soothing visual for a nation still struggling to understand the violence.

More to the point: Polls in the last week have shown that a majority of Americans want to see more civility from their lawmakers; many think less partisan seating is a good idea.

But there’s no guarantee that such chumminess for an hour on television will pay bipartisan dividends when Congress turns to weighty and controversial matters like the fate of Obama’s health care overhaul and the federal spending cuts Republicans promised in the midterm elections.

Conservative interest groups have objected to the mixed seating plan because, they say, it reflects an initial rush to blame activists who use harsh rhetoric.

And a bit of partisan hangover remained from previous years. Justice Clarence Thomas, for example, has said he does not attend the presidential addresses to Congress because they have become partisan occasions, and he was expected to be absent Tuesday night.

Also elsewhere: Justice Samuel Alito, who last year mouthed "Not true" in response to Obama’s criticism of the high court. Alito is the jurist-in-residence at the University of Hawaii law school.

But there were other signs of thaw, some of it inspired by the horror of Tucson.

Chief Justice John Roberts was bringing six members of the high court, quieting speculation that only Democratic appointees to the court would attend.

The Arizona delegation will sit together, around an empty seat to signify Giffords’ absence.

"It is a reminder of how we have to work to bring down crime, how we have to work to build an environment of civility where we can disagree without leading to violence," senior presidential adviser Valerie Jarrett said Tuesday on NBC’s "Today" show.

Conservatives chafed but ignored that comment and mostly agreed to mix it up with Democrats.

Through senior aides, House Majority Leader Eric Cantor late Monday invited Democratic Leader Nancy Pelosi to sit with him for the address. On Tuesday, Pelosi declined, tweeting her thanks to the Virginia Republican and saying she had already asked Rep. Roscoe Bartlett, R-Md.

Dozens of other pairings have been sought and accepted: Sen. Kirsten Gillibrand, D-N.Y., will sit with John Thune, R-S.D. And Rep. Elijah Cummings, D-Md., will sit with Rep. Paul Gosar, R-Ariz., near the rest of that state’s grieving delegation.

Meanwhile, the alleged gunman, Jared Lee Loughner, has pleaded not guilty in the attacks.