First-term Democratic congresswoman Jacky Rosen has formally announced her candidacy for U.S. Senate in 2018. Assuming she secures the nomination, she will take on Republican incumbent Dean Heller, who will be seeking reelection to a 2nd term in the Senate from Nevada. Rosen currently represents that state's 3rd congressional district, which encompasses most of the state south of Las Vegas.
A late June poll from Public Policy Polling showed Rosen and Heller virtually tied, with Rosen ahead 42% to 41%. This will be one of the most watched races of 2018 as it is one of the few realistic opportunities for a Democratic pick-up on a difficult map. Of the 34 seats to be contested in 2018*, 25 of them are already held by Democrats**. Of the nine Republican-held seats, Nevada is the only one in a state not won by Donald Trump in 2016. Aside from Nevada, of the ten races currently seen as most competitive for next year (tan on map below), only Arizona is currently in Republican hands.