Need to Impeach, the advocacy group backed by liberal billionaire Tom Steyer, is trying to increase the pressure on Democratic leadership to get behind impeachment proceedings for President Donald Trump.

This week, The Daily Beast has learned, organizers at the group will kick off a new campaign to target 12 districts held by Democratic lawmakers who do not yet back impeachment. The group plans to spend $360,000 in the first few weeks of the effort, which will fund targeted digital ads, billboards, organizing activities, and events like so-called “Impeach-ins,” which are intended to make the case for impeachment.

The dozen Democrats whom Need to Impeach is targeting are either all prominent members of party leadership or hold positions on key House committees. They include Rep. Jim Clyburn (D-S.C.), the number three House Democrat, Rep. Elijah Cummings (D-MD), the chairman of the House Oversight Committee, and Rep. Hakeem Jeffries (D-N.Y.), the Democratic Caucus Chairman.

Those three members represent heavily Democratic districts where impeachment pressure could build. As sources previously told The Daily Beast, Jeffries was, according to aides, feeling conflicted about impeachment. A spokesman for Jeffries told The Daily Beast on Monday that the Democrat is not "waffling" on the issue.

Clyburn, meanwhile, spent the last week walking back a CNN appearance where he suggested impeachment proceedings were inevitable.

Other lawmakers being targeted by Need to Impeach include Rep. Eric Swalwell (D-CA), a candidate for president and Pelosi ally who sits on the House Judiciary and Intelligence panels; Rep. Nita Lowey (D-N.Y.), who chairs the powerful Appropriations Committee and is another close Pelosi ally; and several Democrats representing liberal districts in southern California and Florida.

Rep. Ben Ray Luján (D-N.M.) is another target. A Need to Impeach source provided an example of a billboard that could soon be going up in his district. “Rep. Luján: We need an impeachment inquiry now,” it reads. The billboard displays the phone number for the D.C. office of Luján, a top member of House Democratic leadership and candidate for Senate, and urges constituents to call in with their thoughts.

The new campaign by Need to Impeach comes as a growing number of House Democrats have begun calling for the launch of impeachment proceedings against the president. The group, along with others organizing for impeachment, believe that building support among voters in progressive districts is key to persuading lawmakers on the fence to take a stand—which would ultimately put pressure on Speaker Nancy Pelosi (D-CA) to take up impeachment, an option she has repeatedly dismissed at this stage. Some 60 Democrats have so far come out in support of launching an inquiry, accounting for a quarter of the party’s House membership.

In a statement, Steyer said that momentum behind impeachment is growing by the day. “The leaders of the Democratic Party deserve to know where their constituents stand, and alongside millions of Americans, we’re calling on them to stop putting political expediency ahead of what’s right,” he said.

Need to Impeach has targeted 47 members of Congress so far this year, and the group says its organizers and volunteers have visited over 100 congressional offices to make the impeachment case. In January, Steyer announced he would pour $6 million into a nationwide ad campaign to boost his message.

The agitating from Steyer has gotten him crosswise with Pelosi, who represents the hedge fund billionaire’s hometown of San Francisco. Steyer has blasted Pelosi’s declaration Trump isn’t “worth” the effort: “Shall America just stop fighting for our principles and do what’s politically convenient?” he asked in a March tweet.

This piece has been updated with additional reporting.