When the Supreme Court convenes for major cases, the line of paid placeholders and interested parties stretches down First Street Northeast hours in advance.

Transparency advocates worked one such scene into a new 30-second TV ad that will run nearly 300 times in the Washington, D.C., market over the next few weeks.

“The Supreme Court’s decisions impact the lives of Americans everywhere, but only a privileged few get to witness history and see justice in action,” the narrator says in the new spot from the Coalition for Court Transparency, an alliance of media and legal organizations calling on justices to allow cameras to televise oral arguments.

The group points to cases of broad public interest, such as recent rulings on marriage equality, voting rights and affirmative action, as examples of when the roughly 400 seats in the courtroom prove inadequate.

“Leading Republicans and Democrats and a large majority of Americans support a simple fix — putting cameras in the Supreme Court,” the narrator continues. “State and federal courts allow cameras in the interest of transparency. Shouldn’t our nation’s top court do the same?”

Senate Judiciary ranking member Charles E. Grassley, R-Iowa, first introduced legislation to open the historically opaque federal judicial system up to cameras 15 years ago.

Following that request, then-Chief Justice William Rehnquist allowed for the release of audio immediately following oral arguments in the Bush v. Gore case that decided the 2000 presidential election. Chief Justice John G. Roberts Jr. has followed suit in a number of high-profile, compelling cases.

Members of Congress have continued to push “cameras in the courtroom” legislation. Rep. Gerald E. Connolly, D-Va., and Senate Majority Whip Richard J. Durbin, D-Ill., currently sponsor versions of the bicameral bill.

Proponents point out that all 50 state supreme courts permit recording equipment to varying degrees. On the federal level, two courts of appeals have allowed cameras in the courtroom. The Judicial Conference of the United States has placed cameras in 14 federal courts as part of a pilot program launched in July 2011 to study the effect of broadcasting federal court proceedings.

Supreme Court justices worry that cameras might lead to grandstanding in the courtroom, or turn them into public figures. While the CCT’s ad casts the Supreme Court as one of the last major institutions of Western civilization that has not embraced 21st-century technology, some justices worry their proceedings would be reduced to entertainment.

SCOTUSblog has compiled a video of the evolving views of Justices Sonia Sotomayor and Elena Kagan on the matter. During their confirmation hearings before Congress, both supported opening the court to cameras. They later rejected the idea.

If views continue to evolve, CCT claims an immediate change is possible. Legal experts agree that the justices can decide today to allow cameras, the group said in a release.

“The idea that such a fundamental function of our judiciary is hidden from the vast majority of the American public does not comport with 21st Century expectations of transparency, no matter what your political leaning,” said Michael Ostrolenk, co-founder and national director of the Liberty Coalition, a CCT member, in the release. “At a time when the public’s confidence in the Supreme Court is eroding, and skepticism in secretive government institutions is high, putting cameras in the Court would be a simple way to help restore the Court’s image.”

The group is sponsoring an online petition asking Roberts to open the proceedings.