Along with Massachusetts, Nevada is one of the few states where Democrats have an opportunity to pick up a Republican-held seat. Several Democrats, including Rep. Shelley Berkley (D) are considering a run. Berkley has said she will decide by the summer. Other possible Democrats include Secretary of State Ross Miller, and state Treasurer Kate Marshall. Attorney General Catherine Cortez Masto is a name to watch as well, as she enjoys broad appeal and could potentially raise large sums of money from Latino and women's groups. The statewide Democratic officeholders have said they would defer to Berkley, if she chooses to run. In his email, Heller seemed prepared to contrast himself with Berkley, should she run. "I stood up to former President Bush, then Senator Obama, and Washington special interests and said no to the Wall Street bailout. In fact, I was the only member of the Nevada delegation to vote against the Wall Street bailout, not once but twice," Heller wrote. Nevada GOP Chair Mark Amodei is likely to step down from his post to run for Heller's congressional seat. Former USS Cole Commander Kirk Lippold has also been mentioned and Krolicki and Angle remain possibilities, if they don't run for the Senate. Heller's seat leans Republican -- but Sen. John McCain (R-Ariz.) only won this district by 89 votes in 2008. If there's a split in the GOP or a potentially divisive candidate, like Angle emerges, it could give Democrats an opening. -- Jessica Taylor and Julie Sobel contributed to this report.