NEW YORK (AP) — A Duke University team expects to have a product available for election year that will allow television networks to offer real-time fact checks onscreen when a politician makes a questionable claim during a speech or debate.

The mystery is whether any network will choose to use it.

The response to President Donald Trump's Jan. 8 speech on border security illustrated how fact-checking is likely to be an issue over the next two years. Networks briefly considered not airing Trump live and several analysts contested some of his statements afterward, but nobody questioned him while he was speaking.

Duke already offers an app, developed by professor and Politifact founder Bill Adair, that directs users to online fact checks during political events. A similar product has been tested for television, but is still not complete.

The TV product would call on a database of research from Politifact, Factcheck.org and The Washington Post to point out false or misleading statements onscreen. For instance, Trump's statement that 90 percent of the heroin that kills 300 Americans each week comes through the southern border would likely trigger an onscreen explanation that much of the drugs were smuggled through legal points of entry and wouldn't be affected by a wall.

The Duke Tech & Check Cooperative conducted a focus group test in October, showing viewers portions of State of the Union speeches by Trump and predecessor Barack Obama with fact checks inserted. It was a big hit, Adair said.

"People really want onscreen fact checks," he said. "There is a strong market for this and I think the TV networks will realize there's a brand advantage to it."

If that's the case, the networks aren't letting on. None of the broadcast or cable news divisions would discuss Duke's product when contacted by The Associated Press, or their own philosophies on fact checking.

Network executives are likely to tread very carefully, both because of technical concerns about how it would work, the risk of getting something wrong or the suspicion that some viewers might consider the messages a political attack.

"It's an incredibly difficult challenge," said Mark Lukasiewicz, longtime NBC News executive who recently became dean of Hofstra University's communications school.

Adair said the system will be automated. Mindful that many politicians repeat similar claims, the database will be triggered when code phrases that have been fact-checked before come up. An onscreen note would either explain that a claim is false or misleading and direct viewers to a web site where they can find more information, or provide a succinct explanation of why it is being challenged. He envisions an average of one fact check popping up every two minutes. A network using the service would likely air the speech or debate on a delayed basis of about a minute.

Lukasiewicz said network executives would likely be wary of letting an outside vendor decide what goes on their screen. Adair said anyone who uses the system would be given veto power over what information is being displayed.

CNN and MSNBC have been most aggressive in using onscreen notes, called chyrons, to counter misleading statements by Trump, although neither did during the border speech. Among the post-speech analyses, Shepard Smith's rapid-fire reality check on Fox broadcast during the three-minute pause before Democrats spoke was particularly effective. But critics like the liberal watchdog Media Matters for America said anyone who turned the coverage off when Trump stopped speaking was exposed to no questioning of his words.

"There is a responsibility to not just be a blind portal and just let things go unchallenged," said David Bohrman, a former CNN Washington bureau chief who consulted on MSNBC's 2016 election coverage. "The goal is a good one. The execution is a challenge."

A technical junkie, Bohrman said he explored different approaches for real-time TV fact-checking while at CNN, but they ultimately proved too complicated and cumbersome.

For networks, an incorrect onscreen fact-check would be a public relations disaster. Politicians also make many statements that a critic might question but isn't necessarily factually incorrect. For example, Trump's contention that there is a "crisis" at the southern border: is that a fact or matter of interpretation?

Rest assured, people will be watching. Very carefully.

Even Tim Graham, director of media analysis at the conservative Media Research Center, concedes that "we all understand that President Trump has a casual approach to factivity."

But conservatives are deeply suspicious that Trump's words are being watched more carefully than those of Democrats. They will notice and take offense if Trump is corrected on the air much more than his rivals, he said, no matter if Trump actually makes more false or misleading statements.

"People aren't going to trust you," he said, "because they know what the objective is. The objective is to ruin the president."

Adair stressed that his product is non-partisan. He believes television networks will catch on at some point because they will realize that their viewers want quick fact-checking.

"Anyone who criticizes will get criticized for criticizing," Bohrman said. "But the reality is we may be able to help the viewers."