Sen. John Ensign has yet another matter to add to his growing list of re-election problems. In addition to a Senate ethics probe and lagging poll numbers, a once-reliable base of support — D.C. lobbyists — has quietly started pushing party leaders to get the Senator to exit the race altogether.

Just when the Nevada Republican needs their fundraising help the most, many K Streeters who run in high-dollar circles have complained that the Senator’s effort is a distraction and that giving to his coffers may be a waste of money, especially when control of the Senate is up for grabs.

“We need to hold that seat,” one Republican lobbyist explained. “I couldn’t give him money. Why waste the resources?”

This lobbyist added that as Ensign’s ethics problems continue from a scandal involving an affair the Senator had with a former aide, K Streeters don’t want to see their donations end up funding Ensign’s legal bills. “Everybody’s throwing their support to Heller,” he said, referring to Rep. Dean Heller, a likely primary challenger to Ensign.

A poll released last week showed Heller beating Ensign in a theoretical matchup.

Other GOP lobbyists said they are taking their complaints directly to National Republican Senatorial Committee Chairman John Cornyn (Texas).

At a recent NRSC fundraiser with Cornyn, several lobbyists urged the chairman to get Ensign out of the race, sources said. The lobbyists have been feeling the pressure from Ensign’s fundraising operation to donate, and they suggested to Cornyn that it wasn’t in the party’s best interest to give the Nevadan money.

“There is a problem with dangerous, vulnerable Members like John Ensign, who most people downtown don’t believe has cleared his name,” another Republican lobbyist said. “We’re all asking, ‘What are you doing?’ And we’re asking [the NRSC], ‘What are you guys doing to deal with this?'”

An NRSC spokesman declined to comment.

But sources familiar with the conversations said Cornyn explained that decision was up to the voters of Nevada.

And Cornyn has said as much publicly.

“The NRSC chairman is selected by the Republican Conference, and I work with the Republican Conference, meaning all the incumbents,” Cornyn told reporters last week. “I would say I learned some important lessons the last cycle, and the most important lesson is the nominee will be chosen by the primary voters in Nevada and nobody else. And so we’ll await their judgment.”

Not all of Ensign’s support downtown has deteriorated.

Tax lobbyist Kenneth Kies, managing director of the Federal Policy Group, got to know Ensign when the Senator was a House Member serving on the Ways and Means Committee. At the time, Kies was chief of staff for the Joint Taxation Committee.

“I’ve told Ensign I’d be happy to support him just like I have before,” Kies said.

The lobbyist added that “Cornyn’s been clear that he doesn’t get involved in these things.”

Still, one Republican source said that at an Ensign D.C. fundraiser last week at Cava Restaurant, turnout was low.

Asked about the number of attendees at the event and about Ensign’s support among downtown lobbyists generally, spokeswoman Jennifer Cooper said her boss is “having good success in lining up fundraisers.” She added that Ensign “expects to have a very productive first six months.”

Even if the Wednesday fundraiser at Cava featured a small crowd, the embattled Senator will take another crack at K Street’s generosity on March 2. According to an e-mail invitation, the political action committees for AT&T, Verizon and CTIA are holding a dinner at Carmine’s restaurant.

Some lobbyists liken the Ensign predicament to that of Sen. Lisa Murkowski. Though she did not have an ethics scandal as a backdrop, the Alaska Republican lost in her party’s primary last summer. When she launched what seemed to be a long-shot write-in campaign and sought K Street cash for the effort, many lobbyists turned their back on her, even though she was the top member of the Energy and Natural Resources Committee.

Other K Streeters, however, hosted events or wrote her checks.

“She definitely knows who her friends are,” one lobbyist said.

Ensign sits on the Finance, Budget and Commerce panels. The latter is of great import for the telecom industry, which is backing the March 2 event.

Even so, another lobbyist whom Ensign solicited said the Senator’s committee slots or status as a sitting Member of Congress don’t matter since his reputation has been tarnished. “Is it helpful if he’s the sponsor of your bill right now? No.”