In Washington, not even picnics are beyond controversy. Certainly not the annual picnic that presidents throw for members of Congress, and certainly not in the days immediately after Congress spanked the president by rejecting one of the top items on his agenda, as the House did last week in sidelining trade legislation requested by President Obama.

But the Obama White House is pressing ahead Wednesday night with this year's version of the picnic, even knowing that all eyes will be on how the president treats the members—especially the Democratic members—who embarrassed him on trade. So pushed to the margins this year will be the usual trivial questions attending the picnic: Which congressmen will be brave enough to don shorts? Which ones will be nerdy enough to wear ties? And, that hardy question of the John Boehner era—will the speaker be caught on camera sneaking a cigarette on the South Lawn as he was at the 2011 picnic?

This year, the only question that matters is this: Will the event become an occasion for a president who abstains from glad-handing to actually press the flesh, twist some arms, and change some minds amid the barbecue and music?

The answer from the White House: Don't count on it.

"I don't anticipate a lot of arm-twisting taking place," insisted White House press secretary Josh Earnest. He called the picnic "a nice opportunity for members of Congress from both parties ... to spend time with their families on a nice summer evening on the South Lawn of the White House. And it is a goodwill gesture and a purely social occasion."

But few events in Washington can ever be "purely social." And no one believes either side of the trade debate can put last week's vote behind them. "It'll be interesting for the Democrats," GOP Rep. Michael McCaul of Texas told National Journal. He predicted "a little tension in the air."

If that's true, then both sides may regret that President Obama has failed to pursue the picnic innovation he championed in 2009 and 2010. In those years, there was a "dunk tank" on the South Lawn. Members of Congress eagerly, and often accurately, tossed balls at a small target that released a lever that sent various senior administration officials into a large tub of water. Among those soaked were Chief of Staff Rahm Emanuel, Legislative Director Phil Schiliro, Budget Director Peter Orszag, and Press Secretary Robert Gibbs. For many members—and a few very envious junior staffers at the White House—it was the highlight of the event and a much-appreciated release of tension.

For members, it was more fun than some of the innovations brought in by other presidents. Jimmy Carter participated in a square dance in 1977; Ronald Reagan had a barbershop quartet in 1987; George H.W. Bush had fireworks in 1990; and Bill Clinton brought in carnival rides, much to the delight of the children in attendance.

Because so many children are there, it has not always been a great venue for lobbying. "People are aware of background dynamics," said Democratic Rep. Gerry Connolly. "But generally this is kind of a family-friendly, festive occasion. And partisan and political policy and ideological differences are kind of left at the gate. That has been my experience, and I would not expect this one to be any different."

Connolly, who is bringing his wife and 24-year-old daughter this year, recalled his first picnic, which came in the middle of the health care debate. He said that debate was kept out of the picnic.

The president always uses the event to praise the families for putting up with having a politician in their midst. And he has grumbled that he has found it of little use in winning over political foes. "When I'm over here at the congressional picnic and folks are coming up and taking pictures with their families, I promise you, Michelle and I are very nice to them and we have a wonderful time," Obama groused at a 2014 press conference. "But it doesn't prevent them from going onto the floor of the House and blasting me for being a big-spending socialist."

Democratic Rep. Brad Sherman, attending this year with his wife and three daughters, dismissed the notion that the trade vote will affect the picnic. "I don't think the picnic will be any different. I don't think the atmosphere will change," he said. "I don't think anybody will, as they did at the baseball game, chant, 'TPA' or 'TPP.'" He added, "We do this for a living. We do it year in and year out, and we will have a good picnic and the atmosphere will be very good."

Rep. Raul Grijalva, cochair of the Progressive Caucus, which has lobbied against Obama's trade policy, admitted that it's difficult to set politics completely aside. "I think it will be in the corners," said Grijalva, who cited a prior commitment that will keep him away from the picnic. "But I don't think it'll be set aside."

The biggest worry of most attendees, though, has nothing to do with any votes. "We're ready to have a festive time," said Rep. Xavier Becerra, chairman of the House Democratic Caucus. "The worst thing that can happen is high humidity."

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