Sen. John Ensign (R-Nev.) has ramped up his fundraising operation amid growing concerns by GOP strategists that polls show him losing to every potential Democratic challenger.

Ensign has held several fundraising events in Washington in recent weeks, including one at the National Republican Senatorial Committee headquarters. He's set to hold another fundraiser Wednesday night at a Capitol Hill restaurant. And these events, Ensign told The Ballot Box, are just the beginning.

Despite the scandal that has hamstrung his second Senate term, Ensign said the response from his supporters "back in Nevada's been very good." Still, he doesn't expect the campaign cash to start pouring in for a few months.

"I think most of the money is going to come in in the second quarter, but we're getting it all scheduled, which is a very positive sign," he said. "We are focused on fundraising right now, and doing my job for the people of Nevada trying to help the economy because it's in dire shape out there."

Ensign's poll numbers have taken a hit since he admitted in June 2009 to having an affair with the wife of one of his top aides. He's currently under investigation by the Senate Ethics Committee for allegedly helping the aide, Doug Hampton, land work as a lobbyist.

Ensign is running for a third term but said a formal launch to his campaign is a "long way off," and in the meantime he's bracing for a tough primary.

The senator said he wasn't sure if Rep. Dean HellerDean Arthur HellerThe Hill's Morning Report — Sponsored by PhRMA — GOP lawmakers race to find an immigration fix 13 GOP senators ask administration to pause separation of immigrant families The Hill's Morning Report — Sponsored by PhRMA — Defiant Trump meets with House GOP amid border blowback MORE (R-Nev.), who has almost $815,000 in his campaign account, would mount a challenge against him.

"I don't know if it will be Heller, but we're expecting a primary challenge, sure," said Ensign, who started 2011 with about $225,000 in the bank, having had to spend hundreds of thousands of his campaign funds on legal bills. "Don't know who it will be, but you can't control that. I think most members are expecting primary challenges."

Asked if personal issues would dominate the primary campaign, Ensign sounded resigned. 

"You'll have to ask [the challengers]," he said. "I think that people in Nevada are pretty happy with the way I voted."

Meanwhile, Ensign said he didn't expect Senate Majority Leader Harry ReidHarry Mason ReidAmendments fuel resentments within Senate GOP Donald Trump is delivering on his promises and voters are noticing Danny Tarkanian wins Nevada GOP congressional primary MORE (Nev.) would join the chorus of his critics.

"We have a friendship; a good relationship," he said. "We still have a great relationship. And our agreement is only not to criticize each other, we don't have like a truce, we just have an agreement not to criticize each other and we've stuck by that, and we'll continue that because it's really important that he and I work together for our state.

"When you have a small state, especially, it's important whoever's in office for you to work together on your issues that affect your state. You can disagree on the big national issues, but there's a lot of issues that affect your state that you need to work together on and we continue to do that."