In judging whether the already clichéd “charm offensive” by President Barack Obama is built to last, it’s best to disregard the readouts from the president’s the-meal’s-on-me meetings last week. His dinner with a dozen Republican senators and lunch with Wisconsin Rep. Paul D. Ryan were only a prelude to the main event this week.

No, it’s not his visit to the Capitol Tuesday to meet with the Senate Democrats, nor his return trip Wednesday to address the House GOP Conference, nor his third foray up Capitol Hill in as many days on Thursday, when he’ll meet with all the Senate Republicans (and separately with the House Democrats, so he can say he touched all the bases).

Much more than any of these, the event that will define the White House-Congress dynamics for the legislative season ahead — on spending, taxes, entitlements, immigration, gun control and Obama’s efforts to remake his cabinet and the federal bench — comes on Wednesday night.

That’s when Obama will speak at a downtown hotel to a couple hundred activists and big-money donors gathered for an inaugural “summit” of Organizing for Action. The OFA, which used to stand for Obama for America, was created by the top veterans of his political team in hopes of putting the grass-roots zeal, fundraising network and even the acronym of the president’s national campaigns to work advancing his agenda.

Plenty of attention will be paid, and deservedly so, to any evidence that the new OFA has been designed to create some form of pay-to-play access for Obama’s top supporters. Meanwhile, for members of Congress looking for a sign that the president’s posture of collegiality and outreach is for real, it’s the text of that public speech that will matter more than anything he might say behind the closed doors of the four caucus meetings or over crab risotto at the Jefferson Hotel.

The more difficult course, but one that might make even the most skeptical Republicans take notice, would be to tell his acolytes that he’s sticking with his revived enthusiasm for bargaining — and that some of the passions they share will have to be tempered to the realities of divided government. Or he could do the easier thing and reward his well-heeled base by reprising the partisan hauteur from so much his last campaign, pledging to hew to his definition of a “balanced approach” no matter what the GOP says.

Most likely, he’ll be willing to leave everyone in Washington with a decent case of cognitive dissonance the next morning. For Obama, the best outcome would be saying just enough to keep his supporters mollified and the Republicans expectant.

The worst outcome would be to have his Democrat friends read surrender in the same words that his GOP critics interpret as evidence of an impending double cross.