“Build the wall!" That chant became a frequent rallying cry at rallies for Donald Trump, who vowed to stem illegal immigration by building a wall along the U.S.-Mexico border. The candidate, now president-elect, would routinely engage in a back-and-forth with crowds. "Who's going to pay for it?" Trump would ask. "Mexico!" they'd shout back.

Not so, as it turns out. In an APNewsBreak, congressional correspondent Erica Werner and new White House reporter Jill Colvin were the first to report that Trump and congressional Republicans were exploring ways to use existing law – and U.S. taxpayer dollars – to build the border wall.

Their scoop earns the Beat of the Week.

Last Thursday, Werner was working on another story when votes got under way in the U.S. House. For reporters, this is like the bell to signal dinner. Everyone heads to the House to talk to lawmakers during votes.

Werner had been asking about the border wall since December when she heard rumblings about using taxpayer dollars.

As is the custom of AP congressional correspondents, Werner made her way across the Capitol from the Senate to the House by walking on the second floor – past the Senate majority leader's office, through the Rotunda and past the House speaker's office. She had been asking about the border wall since December when she heard rumblings about using taxpayer dollars.

On that brief walk, Werner encountered several of her best sources and she learned about the discussions between team Trump and congressional Republicans. She immediately rushed back to the Senate press gallery, and reached out to Colvin, who contacted her sources in the Trump camp. Confirmation from three sources allowed the AP to be first in reporting the news.

Ap16314104096738 1240

Tomas Munoz and Marta Saenz embrace near where the border wall meets the Pacific Ocean, Nov. 8, 2016, in Tijuana, Mexico.

AP PHOTO / GREGORY BULL

As the story said: “Under the evolving plan, the Trump administration would rely on existing legislation authorizing fencing and other technology along the southern border. Congress would be asked to ensure that enough money is appropriated to take additional new steps – but would not pass a stand-alone bill authorizing a big new wall.... The approach could come as a surprise to some but could avoid a legislative fight Trump might lose if he tried to get Congress to pass a stand-alone bill authorizing the kind of border wall he promised during the campaign.”

The APNewsBreak on the story – beat Politico by an hour and 43 minutes. The Washington Post credited the AP. Other news organizations caught up the next day when the president-elect responded on Twitter, saying Mexico will reimburse taxpayers for a new border wall and that U.S. money spent will be for the "sake of speed."

For their aggressive reporting on a story revisiting one of Trump's most pronounced campaign pledges, Werner and Colvin share this week's $500 prize.