Supreme Court nominee Judge Brett Kavanaugh looks at U.S. President Donald Trump in the East Room of the White House in Washington, U.S., July 9, 2018.

The Judicial Crisis Network, a conservative group, announced Tuesday that it will spend $1.1 million in a two-week national ad campaign to pressure Democratic presidential candidates into releasing a short list of potential Supreme Court nominees compiled by liberal groups.

The campaign comes in response to a report in The New York Times about liberal groups compiling a list of young liberal judges qualified for judicial appointments. The report noted that the list will not be made public, unlike the short list of potential Supreme Court nominees that President Donald Trump released during the 2016 campaign. Trump's list was compiled by individuals affiliated with conservative groups, including The Heritage Foundation and The Federalist Society.

"Tell Joe Biden: Trump released his list," the new ad says. "Why won't you?"

It's not clear that Democratic candidates for president, who are avoiding talking about the list, have seen it. The initiative behind it is called Building the Bench and is being underwritten by the Alliance for Justice, a 40-year-old liberal advocacy group, as well as other organizations, according to the Times. Alliance for Justice did not respond to a request for comment.

"It is essential to be ready on Day 1 of a new administration with names to fill every vacancy," Nan Aron, the alliance's president, told the Times. "This is to start identifying people so the new president won't waste a minute in addressing this need."