Democratic congressional leaders last night delivered a few more scathing reviews of President Reagan's performance in the Iran-contra affair but agreed with him to close that show and bring pressing budget and foreign policy issues onto the national stage.

In the official Democratic Party response to Reagan's televised address, Sen. George J. Mitchell (D-Maine) told the nation that Democrats hold Reagan "personally responsible" for the "serious mistakes" in selling arms to Iran. But Mitchell said Reagan was right in asserting that the whole affair "should be put behind us."

Mitchell, a leading member of the joint Iran-contra investigating committee, declared that "the major mistakes were in the policies themselves and the policies were the president's."

But he responded to Reagan's plea for bipartisanship by saying that "we want to work with the president in a spirit of mutual trust." He and Senate Majority Leader Robert C. Byrd (D-W.Va.) challenged Reagan to negotiate a compromise with Congress on budget-deficit reduction now, rather than wait for the balanced-budget constitutional amendment Reagan urged in his speech.

While such Republican presidential hopefuls as Rep. Jack Kemp (N.Y.) and former senator Paul Laxalt (Nev.) endorsed Reagan's call for refocusing on the unfulfilled goals of his administration, Mitchell, in stern tones, sought to underline the shortcomings of the president's performance in the Iran affair.

The former federal judge said Reagan "personally approved, in writing, the sale of weapons to Iran." Mitchell said that has increased the danger that American sailors in the Persian Gulf "face the terrible possibility of attack by a nation we've helped to arm."

Mitchell also said "the president personally approved, in writing, the exchange of arms for hostages," a decision he said left America's antiterrorism policy "in ruins" and "as many Americans now held hostage in Lebanon as there were when this effort began."

Despite such harsh indictments, House Majority Leader Thomas S. Foley (D-Wash.) told television interviewers that the Democrats never "intended to make this a major campaign issue."

Instead, the Democrats rushed to take up Reagan's challenge on the deficit -- and conspicuously ducked the issue of Supreme Court nominee Robert H. Bork, whose confirmation Reagan named first on his agenda.

Neither Mitchell nor Byrd chose to react to Reagan's plea for a quick Senate vote on the confirmation of Bork, the controversial and conservative appeals court judge Reagan said had never been reversed by the Supreme Court.

Rather than debating Bork's merits, the Democrats seemed eager to play pin-the-deficit on Reagan. While the president plugged again for a balanced-budget amendment as the only sure way to stop spending pressures, Byrd said, "What we need is for this president to work with Congress now to attack the triple-digit deficit and the doubling of the public debt, which happened on his watch."

None of the Democrats seemed impressed by Reagan's offer to negotiate all spending items in return for an up-and-down vote this year on the balanced-budget amendment. Foley said he sees no reason to think the measure, which failed while Republicans still controlled the Senate, has gained support.

Sen. Paul Simon (Ill.), a Democratic presidential hopeful who supports the balanced-budget amendment, said that "not once in 6 1/2 years has the White House lent a hand for serious steps to stop the borrowing binge."

Former Arizona governor Bruce Babbitt, another Democratic presidential contender, said, "I wish he {Reagan} had been more contrite about his role in the Iran-contra affair and more honest about what it will take to get America's economic future back on track . . . . A constitutional amendment to balance the budget is as hopeless as selling arms to the ayatollah."

On Central American policy, Reagan found himself drawing praise from Democrats and a degree of criticism from some fellow Republicans. Mitchell said Democrats were "encouraged by recent progress toward peace in Central America," applauding Reagan's support of separate proposals for ending the struggle in Nicaragua, advanced by House Speaker Jim Wright (D-Tex.) and by the leaders of other countries of Central America.

By contrast, Kemp said he is "gravely disappointed that the president did not forcefully restate his principle of continued military aid to the freedom fighters if democracy and freedom are to be achieved in Nicaragua."

Staff researchers Michelle Hall and Colette Rhoney contributed to this report.