Seeing an opportunity to build on the “cut spending” mantra currently in vogue in Congress, Sens. Pat Toomey (R-Pa.) and Claire McCaskill (D-Mo.) introduced legislation today that would permanently ban earmarks.

But with powerful opposition to further curb earmarks, including from Senate Majority Leader Harry Reid (D-Nev.), the proposal to limit Member-directed spending is unlikely to get a vote any time soon.

“There is an effort under way to go back to earmarking as usual as it used to be, and I think that would be a disaster for our Congress, and we intend to do our very best to prevent that,” Toomey said at a press conference today. “We can’t afford to waste money this way. … We are on a fiscal trajectory that can only lead to disaster if we don’t change this path.”

At the beginning of this year, lawmakers agreed to take a two-year break from the practice of Members directing money to particular projects in the annual spending bills.

House Republican leaders led the push for the ban when they won the majority in the last election after campaigning on cutting Washington spending. But Senate leaders in both parties resisted the moratorium until Minority Leader Mitch McConnell (R-Ky.) in November 2010 bowed to pressure from within his Conference and signaled he would go along with it. Until that point, McConnell had backed earmarks. Senate Democrats subsequently followed suit, announcing a ban in February.

In the 15 years leading up to 2010, Toomey said earmarks tripled and had risen to $33 billion, which amounts to less than 1 percent of the federal budget.

“I’ll acknowledge that $33 billion itself doesn’t put us on a sustainable fiscal path, but we have to start somewhere,” Toomey said.

McCaskill, who is up for re-election in 2012, said she did not campaign against earmarks when she was running in 2006, but said the more she studied the earmark process, the more she found it repugnant.

“When I got here and people began explaining to me, I said, ‘This isn’t right,’” McCaskill said, adding that she declined to participate. “No one could tell me who was making the decision as to who got how much. No one could tell me how that process occurred.”

The lawmakers said the earmark process leads to wasteful spending.

“It’s a process that is designed and exists for the purpose of circumventing the kind of scrutiny and attention and competitive bidding that the spending of taxpayer dollars should always be subject to,” Toomey said. “Worst of all, earmarks became a currency that was used to buy votes. There was an unwritten rule, but it was pretty well enforced, that if somebody asked for an earmark and they got their earmark that they were obligated to vote for that bill regardless of how bloated it was, regardless of how wasteful it was. This should be completely unacceptable in an era where we are running trillion-dollar deficits.”

But earmarking also had its defenders, including Reid and Senate Appropriations Chairman Daniel Inouye (D-Hawaii).

After President Barack Obama vowed in his January State of the Union address to veto legislation that includes earmarks, Reid told NBC News, “This is an applause line, an effort of the White House to get more power. They have enough power as it is.”

In an interview with Roll Call in October, Inouye said he intends to bring back earmarks after the moratorium expires.

“I am going to do everything to reinstate earmarks — or whatever you want to call them — because the Constitution is clear and it was never intended to have the executive branch do all of that. We are the ones who are called up to say to folks, ‘You are going to pay this tax.’ We have to have some say on how to spend it.”

Both see earmarks as a Congressional right bestowed by the Constitution, which gives Congress the power of the purse. They also argue that Members are in the best position to wisely spend funds in their state, as opposed to federal agency bureaucrats.

There are also some Senate Republicans who have also questioned past efforts to curtail earmarking, including Sen. James Inhofe (R-Okla.), Sen. Lisa Murkowski (R-Alaska) and Senate Appropriations ranking member Thad Cochran (R-Miss.).