"There's the potential absolutely of Nevada turning blue this year, if they can get the turnout", said David Damore, a political-science professor at the University of Nevada, Las Vegas. One is Sen Heidi Heitkamp's seat in North Dakota.
Here's a guide of things to watch for in Tuesday's primaries.
Dean Heller.in November, Heller is expected to face Democratic Rep. Jacy Rosen, who is expected to easily win a six-person primary, in the fall. Pete Domenici and Michelle Laxalt, the daughter of former Nevada governor and senator Paul Laxalt.
Three Democratic candidates are vying for their party's nomination - Phil Noble, James Smith and Marguerite Willis.
If Fenty were to win the primary, reflected Condit, "I think she brings something very different to the Republican Party than the state of Virginia Republicans are accustomed to". State Attorney General Janet Mills, who like Giunchigliani has the backing of Emily's List, started the race as the front-runner but has faced tough competition from the large field.
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Locally in the 2nd Congressional District, incumbent Republican Rep. Scott Taylor has some competition. In the 4th District, vacated by retiring Rep. Ruben Kihuen, two former congressmen - Democrat Steven Horsford and Republican Cresent Hardy - are the favorites.
He's facing off against Mary Jones in Tuesday's primary. The other top contenders are former State Department official Alison Friedman, Army veteran Dan Helmer and Lindsey Davis Stover, a former adviser on veterans policy.
For one, Conway Belangia he said, "Both the Democrats and the Republicans have governor's races".
Democrats are also on a long winning streak in Virginia. Two Republican statewide officeholders, Attorney General Alan Wilson and Secretary of State Mark Hammond, also face primary challengers.
Although she narrowly lost Loudoun in the 2016 election, across the 10 District Comstock beat Bennett by almost six points.
The President also tweeted an update of his meetings in Singapore "after a truly awesome visit " and said that "great progress was made on the denuclearization of North Korea".
In the Republican-leaning 7th District, which runs from Blackstone to Culpeper and includes parts of suburban Richmond, Democrats Abigail Spanberger and Dan Ward are seeking their party's nomination to challenge GOP incumbent Dave Brat.
Although Sanford backed key Republican priorities in Congress such as cutting taxes and healthcare, and has been endorsed by major conservatives groups such as the Club for Growth, he has also been vocal with his criticism of Trump when they have disagreed.