WASHINGTON, April 23 — In a vivid display of their new power, Democrats across Capitol Hill approved a flurry of subpoenas today to fuel a series of investigations of the Bush administration.

The House Committee on Oversight and Government Reform issued three subpoenas in quick order. One was to Secretary of State Condoleezza Rice to answer questions about the administration’s prewar claims about Iraq’s weapons programs and two were to the Republican National Committee and its chairman to be questioned about whether the party’s e-mail system was used by Bush officials to conceal some of their actions.

The Senate Judiciary Committee authorized but did not issue a subpoena for Sara Taylor, the deputy to Karl Rove, President Bush’s chief political adviser. The committee wants to question her about the White House role in the dismissal of eight United States attorneys.

And in what could be a significant development in the investigation of those dismissals, the House Judiciary Committee moved toward granting a form of immunity from prosecution to Monica Goodling who was a senior aide to Attorney General Alberto R. Gonzales until her recent resignation.