Dan Janison Melville. N.Y. Tuesday January 26, 2010. Daniel Janison,

Dan Janison has been a columnist at Newsday since 2007.

At national conventions, just a spoonful of amnesia helps the medicine go down.

Since the votes are usually set in advance these days, a chief goal of the gathering is to bury annoying facts, contradictions and past fights — and display “party unity.”

One example: Tuesday’s kumbaya moment between Hillary Clinton and Bernie Sanders gave a hint of photo ops to come at the Democrats’ Philadelphia convention.

But first, the Republicans meet next week in Cleveland — where Donald Trump’s nomination will demand an extra-huge heap of forgetfulness to keep the veneer from cracking.

Delegates and guests will want to forget the 2004 convention where President George W. Bush declared amid the Iraq War: “More than 50 million people have been liberated, and democracy is coming to the broader Middle East.”

They’d best forget that because of Trump’s repeated assertion that Bush lied to get us into Iraq, which he called a disaster. (Trump falsely claimed he never said Bush lied — another mess worth forgetting.)

advertisement | advertise on newsday

The party may wish to forget that Indiana Gov. Mike Pence, on Trump’s short list of possible running mates, said last December: “Calls to ban Muslims from entering the U.S. are offensive and unconstitutional.”

While we’re at it, the GOP faithful should forget the party’s 2008 convention. That year, they listened respectfully as Sen. John McCain told movingly of turning down an offer by his captors in Vietnam to let him go — because, he said, that would violate his obligation to other prisoners and be used as propaganda.

Those who cheered McCain would best forget that Trump, who got a medical exemption from the draft, said only a year ago that McCain’s “not a war hero. He was a war hero because he was captured. I like people who weren’t captured.”

The delegates should forget that McCain — before issuing a minimalist endorsement — blasted Trump’s “uninformed and indeed dangerous statements on national security issues that have been raised by 65 Republican defense and foreign policy leaders.”

They should either forget the 2012 plank demanding quick action on a Trans-Pacific Partnership trade agreement — or ignore Trump’s trashing of such agreements as “no good for us and no good for our workers.”

Of course Mitt Romney, the great Republican hope of four years ago, will be a must-forget -- easily, since he's not due to attend.

Now that Trump is fundraising for his campaign — and purportedly for the party — everyone in the halls and hotels of Cleveland can forget his past promises to the contrary.

“By self-funding my campaign,” Trump tweeted 10 months ago, “I am not controlled by my donors, special interests or lobbyists. I am only working for the people of the U.S.!”

Forget that, too.

Celebration time is coming to Cleveland and difficult facts-- let alone the hard questions they provoke -- would only kill the buzz.