A poll of likely Republican primary voters says Sen. John Ensign, R-Nev., trails Rep. Dean Heller, R-Nev., by 15 points.
The poll of some 600 likely GOP voters was conducted in January and was given a confidence level of plus or minus 4 percent.
The poll prompted Heller's staff to release a memo Tuesday saying he is considering a bid for the seat in 2012 and will announce his decision in the near future.
If Heller does make the jump to a Senate race, that opens the door for Sharron Angle, whom he defeated in the primary for his first term in the House, to again run the vacated congressional seat.
Ensign has said he has every intention of running for and winning another term in the U.S. Senate despite the revelations of his sexual indiscretions with Cindy Hampton, the wife of his best friend and former senior staffer.
Allegations his parents paid the Hamptons hush money resulted in two different investigations into whether Ensign violated the law. One of those is ongoing. The Senate Ethics Committee named a special counsel in the case last month.
According to the memorandum issued by the Tarrance Group on its survey, Ensign is "so badly damaged he is already trailing on a ballot test against Dean Heller by 15 points."
The memo said 53 percent of voters would pick Heller and only 38 percent Ensign.
It says Heller captures 62 percent of "extremely conservative voters" - double the number who go for Ensign. He also took more than half the vote among Tea Party supporters, pro-life Republicans and Second Amendment backers.
"Sen. Ensign has no political or geographic base left among Republicans in the state," the memo states.