CLEVELAND — It’s hard to avoid reporting what a candidate says — especially the nominee of a major political party — even when he or she is lying.  

That’s the great advantage of a soapbox, a convention podium or a 30-second ad: The candidate paid for the right to say anything.  

This has presented a major problem for the media in a cycle in which the Republican nominee for president shamelessly spouts out-and-out lies and casts insidious aspersions on his rivals, like the notion that Ted Cruz’s father had a role in the assassination of John F. Kennedy.

[


Special Coverage: 2016 Republican National Convention


]

There’s no good answer for that: It wouldn’t be right for the media to stop broadcasting Donald Trump or printing the things he says. In fact, it would be a tremendous disservice to discerning voters, who ought to be able to weigh what he’s saying against the truth, and determine whether his mendacity matters when they go to the polls.  

But something so simple as Melania Trump’s relatively innocuous theft of Michelle Obama’s words has pointed out another way the media can fight back against dishonesty in the political sphere.  

Melania Trump, it should be noted, didn’t say anything untrue. But, once she began taking flak for pilfering prose, Trumpville rallied its TV talkers and convention-hall spinners to say she hadn’t stolen a thing.  

“There’s no cribbing of Michelle Obama’s speech. These were common words and values,” Trump campaign chief Paul Manafort said on CNN’s “New Day” Tuesday morning.  

The only true thing Manafort said was that “these were common words and values.” Yeah, common to Michelle Obama and Melania Trump.  

[

Correspondents Committee Defends Media Outlets Banned by Trump

]  

Manafort went even further: “To think that she’d be cribbing Michelle Obama’s words is crazy.” He was the first, but hardly the last Trump surrogate to lie about the episode without an ounce of shame.  

In the old days, reporters would keep track of which sources lied to them and stop quoting those sources.  

That’s how the media should handle Trump now.  

Sure, he could stand behind the podium on Thursday night at the Republican convention, wearing a pair of flaming pants, and lie to the country for an hour about himself, about Hillary Clinton and about public policy. TV stations would rightly broadcast it and reporters would dutifully quote him in their stories. There’s no way around that.  

But his surrogates shouldn’t get any airtime or ink if they’re going to keep lying to the American public. The plagiarism question is a minor one compared to the daily deceptions Trump advocates spew into the air on national television.  

Often, they’re big lies, like the ones Trump tells. To hear The Donald tell it, he’s been right about every world event in the last half century. He was against the Iraq and Libya wars from the start, he and his minions insist, even though he was for both of them before he was against them.  

The danger here is that other politicians and their crews — happy to say whatever they can get away with — will see what Trump does and determine that there’s no cost to lying.  

The media can and should impose a heavy price on liars. It used to be that the cost was public shaming. If a campaign aide lied, a dogged journalist would call the person out and the aide would walk it back or simply stop repeating the same calumny. That clearly doesn’t work anymore.  

[

Disappear, Donald

]  

The next step is to deny oxygen to the lies and the liars — figuratively, not literally. If someone lies a lot, he or she should stop being invited on television, and reporters for print and digital outlets should stop quoting him or her.  

This creates two costs. The first is the obvious one: It’s a lot harder for a campaign to get its message out if the candidate’s aides and supporters don’t get airtime. The second is that most of those talkers want to profit as television commentators or public-relations professionals once the campaigns are over. If they fear that they won’t get TV contracts, or have the ability to influence print reporters because they’re dishonest, maybe they’ll tell the truth a little more often. Or, at least, they’ll stop lying so aggressively.  

Ultimately, there’s no damage to the nation from Melania Trump picking Michelle Obama’s pocket. But the effort that went into lying about it is both worrisome and standard practice for the Trump campaign.  

For all the hand-wringing in newsrooms about how to handle the Trump conundrum, there’s been precious little attention to the levers that the media have to carry out the responsibility of separating fact from fiction.  

The easiest way is to ignore the lies and liars. If they want to be heard, they should have to tell the truth.  

Roll Call columnist Jonathan Allen is co-author of the New York Times-bestselling Clinton biography “HRC” and has covered Congress, the White House and elections over the past 15 years.