After Rep. Mark Souder’s (R-Ind.) confession Tuesday that he had an extra-martial affair with a staff member, House Democrats held their fire and chose not to ignite a new round of rhetorical attacks on Republican ethics — for now.

Democratic aides warned, though, that they by no means plan to give GOP leaders a pass on the House’s latest sex scandal, making it clear that they’ll attempt to force Republican leaders to answer tough questions on what they knew about the affair and when they knew it, just as Republicans did following Rep. Eric Massa’s resignation from the House.

The New York Democrat stepped aside in disgrace last March after allegations surfaced that he sexually harassed several male staffers.

The House ethics committee is investigating what Democratic leaders knew about Massa’s relationships with his staff.

Republicans said they reacted swiftly and sternly with Souder once they were aware of the affair, but Democrats hinted at what the line of inquiry might be.

“This inappropriate relationship between a Member and his staffer was unknowingly subsidized by taxpayers for years,” one Senior Democratic leadership aide said. “The public deserves a thorough investigation into what Mr. Souder’s office and members of the GOP leadership knew, when did they know it and what did they do about it. And why wasn’t the bipartisan ethics committee notified?”

A second senior Democratic aide said, “There are real questions over what the Republican leadership or other Republicans knew, when they knew it and why they didn’t contact the ethics committee, and the public needs to hear those questions answered.”

But GOP aides said House Minority Leader John Boehner (R-Ohio) alerted the ethics committee as soon as he learned about Souder’s affair.

Majority Leader Steny Hoyer on Tuesday dismissed comparisons between the Republican leader’s handling of the Souder incident and Democratic leaders’ response to Massa’s transgressions, saying the two situations were not analogous.

“They are two different situations, entirely different,” the Maryland Democrat said.

And Hoyer defended Democrats’ response to revelations regarding Massa, saying he urged Massa to go to the ethics committee as soon as he learned of the allegations against him.

“He went, and three weeks later, he was gone,” Hoyer said.

Hoyer said Republicans were ignoring the fact that Republican leaders knew about former Rep. Mark Foley’s (R-Fla.) inappropriate behavior from the late 1990s until the fall of 2006, when the news broke that he’d had relationships with male pages, and “did nothing.”

But as the details of Souder’s affair with part-time aide Tracy Jackson came to light Tuesday, they did not appear to have the complicated and, at times, bizarre twists that fueled the Republican crusade in the Massa case or the election-changing effect of the Foley scandal in 2005. But the details of Souder’s relationship with Jackson remained murky, including how long the relationship had gone on.

Rumors about Souder and Jackson had apparently circulated during his recent primary, but last week Boehner’s staff began to receive calls from reporters asking about the validity of the allegations, according to several House Republican aides.

Souder’s staff briefed Boehner’s staff about the situation Sunday. When Souder and Boehner spoke the next day, Boehner indicated that the Indiana Republican should resign.

Boehner spokesman Michael Steel declined to comment on the specifics of the conversation but said, “Boehner has been perfectly clear that he will hold our Members to the highest ethical standards.”

Following his conversation with Souder, Boehner sent a letter to the House ethics committee, formally known as the Committee on Standards of Official Conduct, to notify it that he had learned of the affair, according to GOP aides familiar with the letter.

Souder said in a statement Tuesday that he planned to submit his official resignation to Speaker Nancy Pelosi (D-Calif.) on Friday.

“I sinned against God, my wife and my family by having a mutual relationship with a part-time member of my staff,” Souder said a tearful press conference Tuesday.

“In the poisonous environment of Washington, D.C., any personal failing is seized upon, often twisted, for political gain,” he said. “I am resigning rather than to put my family through that painful, drawn-out process.” But even before his announcement Tuesday, Souder seemed ready to call it quits in Congress.

In an interview last month, shortly before his victory in a bitterly contested primary, Souder told the political website Howey Politics Indiana: “I’ve been miserable. … I was thinking this was going to be my last term.”

Souder told the website that concerns about his health and the limited time he gets to spend with his family were pushing him toward retirement.