A top Senate Democrat is pushing to hand the Justice Department more firepower to fight public corruption, even as a handful of House Democrats appear to be coming under new scrutiny in a federal probe of earmarks and campaign contributions.

Senate Judiciary Chairman Patrick Leahy (D-Vt.) has dusted off a measure he wrote two years ago that authorizes an additional $100 million for federal prosecutions of corruption cases. The measure, co-sponsored by Sen. John Cornyn (R-Texas), would also give the feds more time to uncover Congressional wrongdoing and would tighten anti-corruption laws.

Leahy’s panel is set to mark up the bill today, although it could be punted to next week. In the House, Rep. Hank Johnson (D-Ga.) plans to offer a companion measure, an aide said.

Whether the package will get anywhere is a separate question.

With Democrats now firmly in control of both chambers, the party is struggling to deal with ethics issues of its own just two years after tarring the GOP as the party of corruption.

Most recently, FBI raids of firms with close ties to Rep. John Murtha (D-Pa.), the defense spending chief in the House, suggest federal agents are homing in on the connection between earmarks and campaign contributions. Rep. Jeff Flake (R-Ariz.) tried on Wednesday afternoon to force an ethics investigation into that nexus, but lawmakers voted largely along party lines to rebuff his attempt.

Considering the circumstances, Democratic leaders are likely loath to help prosecutors build their cases — a fact some supporters of the measure acknowledge privately.

Leahy’s measure made it out of committee in November 2007 but never came to the floor. In the House, a companion bill offered by Johnson languished in subcommittee.

The measure would tighten ambiguities in the law, opened by recent court decisions, by clarifying what constitutes an illegal gratuity and broadening the definition of an official act. And it would give investigators more time to track down bribery, honest-services fraud and extortion by extending the statute of limitations on those crimes from five years to six.

“If we are serious about addressing the kinds of egregious misconduct that we have witnessed over the past several years in high-profile public corruption cases, Congress should enact meaningful legislation to give investigators and prosecutors the tools and resources they need to enforce our laws,” Leahy said in a statement when he reintroduced the bill on Jan. 6, the first day of the new Congress.

It is not yet clear whether the Justice Department is embracing the proposal. A spokesman did not return a call for comment.

Government reform advocates are rallying behind it, arguing that it would offer prosecutors critical tools to root out corruption. Democracy 21, Public Citizen and three other groups penned a letter on Wednesday urging Senate Judiciary members to support it.

Ethics lawyers, on the other hand, whose clients could face more and tougher prosecutions if the measure passes, have called it unnecessary.

“They’re always overkilling, and yet the prosecutor has a quiver full of arrows already,” defense attorney Stanley Brand said.

While corruption cases have made plenty of headlines in recent years, prosecutions of those crimes actually fell 14 percent during President George W. Bush’s presidency as feds focused on anti-terrorism efforts, according to a 2007 report by the Transactional Records Access Clearinghouse at Syracuse University. Already, President Barack Obama’s Justice Department has signaled its intention to shift its focus — to prosecuting corporate misdeeds in the wake of the Wall Street meltdown.