Bipartisan momentum is building for legislation that would give reporters new legal protections from government authorities who want them to reveal their confidential sources. But it’s far from clear whether the effort can overcome the objections that derailed similar bills in the Senate in 2007 and 2009.

Reps. Ted Poe, R-Texas, and John Conyers Jr., D-Mich., appeared with a group of lawmakers from both parties Wednesday to announce growing House support for “media shield” legislation (HR 1962) that would create a judicial process to ensure that reporters are not compelled to identify their sources unless certain conditions are met. The conditions include requiring government investigators to prove that “the public interest in compelling disclosure outweighs the public interest in gathering or disseminating news or information.”

Poe and Conyers, members of the Judiciary Committee, said the legislation is a response to recent revelations that the Justice Department took phone call records and other information from reporters with The Associated Press and Fox News as part of broader investigations into government leaks.

The Justice Department’s actions, Poe said, “remind me of the old Soviet-style tactics of spying on the press.” He added that lawmakers from both parties “believe it’s time for Congress to intervene and take action to preserve and protect the First Amendment that we all believe in.”

Conyers, the top Democrat on the Judiciary panel, said the legislation would protect the constitutional rights of the media and send a strong message that “fishing expeditions” by the Justice Department into the professional dealings of the press “are not in order.”

The House bill has 16 co-sponsors, including 14 members of the Judiciary Committee, ranging from conservative Republican Howard Coble of North Carolina to progressive Democrat Jerrold Nadler of New York. Judiciary Chairman Robert W. Goodlatte, R-Va., and Speaker John A. Boehner, R-Ohio, both signaled Wednesday that they could be supportive of the measure since they backed similar efforts in the past.

Boehner’s spokesman, Michael Steel, said he wasn’t familiar with the details of the Poe-Conyers proposal but noted that Boehner “supported a bill on this topic that passed the House in 2007.” Poe said Wednesday that his legislation is “very similar to the bill in 2007.”

The bipartisan momentum is not limited to the House. In the Senate, Charles E. Schumer, D-N.Y., and Lindsey Graham, R-S.C., are co-sponsoring similar media shield legislation at the behest of President Barack Obama, who has been on the defensive regarding the actions of his Justice Department in the AP leaks probe.

Thorny Questions

Bipartisan support for media shield legislation, particularly in the House, is nothing new. The House overwhelmingly passed similar bills in 2007 and 2009 — the latter measure by a voice vote — only to see those bills falter in the Senate.

The same dynamic could still be at play as lawmakers, particularly in the Senate, wrestle with thorny questions over who should be defined as a “journalist” and when the government may override the shield law and compel the disclosure of a reporter’s sources.

In the current House bill, journalism is defined as “gathering, preparing, collecting, photographing, recording, writing, editing, reporting or publishing of news or information that concerns local, national or international events or other matters of public interest for dissemination in the public.” That definition is almost certain to run into concerns among senators, including Richard J. Durbin, D-Ill., and Dianne Feinstein, D-Calif., who expressed wariness in 2009 about an overly broad definition of journalism — one they said could allow congressional press secretaries or bloggers to claim a reporter’s privilege in court.

Asked about the senators’ past concerns on Wednesday, Poe acknowledged the difficulty in defining journalism under the bill. “Probably before we get a vote on the bill, we’ll clarify what a journalist is,” he said. “Because of the Internet primarily, 2007 is a lot different than 2013.”

Concerns over national security are likely to be the other major obstacle. Schumer previously pushed the media shield legislation he is currently sponsoring, but the measure — which made it out of the Senate Judiciary Committee on a 14-5 vote in October 2009 — eventually fell victim to concerns over national security.

In particular, a furor over the website WikiLeaks, which published sensitive national security information as the bill was pending on the Senate floor, led lawmakers to question whether the measure would allow the site’s founder, Julian Assange, to avoid prosecution.

“It just never went forward from there,” said Gregg Leslie, legal defense director for the Reporters Committee for Freedom of the Press, which has advocated for a federal media shield law to rival the measures that are already on the books in 49 states and the District of Columbia.

Leslie acknowledged the difficulty in passing highly technical legislation that attempts to strike a balance between national security and freedom of the press, but he said he believes the chances this year are better than in the past.

He noted there is bipartisan outrage in Congress about the Justice Department’s actions, and several key senators who held up passage of the bill in the past — such as Jon Kyl, R-Ariz., and Arlen Specter, D-Pa. — are no longer in Congress. In addition, new senators, such as Republicans Rand Paul of Kentucky, Mike Lee of Utah and Ted Cruz of Texas, are strong proponents of the Bill of Rights and might be inclined to support the measure based on its First Amendment protections.

“I would think that’s going to work in our favor,” Leslie said.

In an earlier version of this article, the photo caption misstated which chamber Ted Poe serves in. He is in the House.