While Democrats are preparing for a potential "blue wave" to take control of the House of Representatives in the November 6 midterms, there is a much narrower and less likely path to victory in the Senate.
There are 35 Senate seats up for grabs Nov. 6, but only nine belong to Republicans -- a small crop from which to pluck. Democrats could steal some races, but there are some Democrat-controlled seats that could also go the GOP.
Here is a look at the tightest races heading into the Nov. 6 midterms.
Democrat Senate seats in most danger
Nelson is currently the only Democrat in a Florida statewide-elected office. Scott is running for senator after two terms as Florida governor. Nelson first won this seat in 2000. Trump won Florida by 1.2 percent over Clinton, but nothing in this swing state is ever a sure thing.
Donnelly made a surprise move in a TV ad by showing a moment when President Trump praised him by name. It happened when Trump signed into law legislation to allow people with life-threatening illnesses to bypass the Food and Drug Administration to get experimental drugs. Braun is businessman who resigned as state representative to focus on this race.
McCaskill is seeking her third term from a state that hasn't voted a Democrat for president since 1996. Hawley is the Missouri attorney general. There is also an independent, a Libertarian, and a Green Party candidate on the ballot, which makes things even more interesting if the vote is tight.
Scandals have followed Menendez in this race. He was admonished by the Senate Ethics Committee for accepting gifts and advocating for the donor's personal and business interests, and was acquitted of campaign bribery and fraud charges earlier this year. Hugin recently revived a 2012 claim that Menendez had sex with underage prostitutes in the Dominican Republic -- something an FBI investigation did not corroborate. Those have helped make this race tighter than expected, given that a Republican hasn't been elected to the Senate from New Jersey since 1972.
Heitkamp -- a Democratic senator in a state where President Trump defeated Hillary Clinton by a more than a 2-to-1 margin -- has some tough sledding. Her decision to vote against the confirmation of Brett Kavanaugh for the U.S. Supreme Court may have made it even tougher. Cramer is currently North Dakota's lone member of the House of Representatives.
Republican Senate seats in most danger
This is the seat Republican Sen. Jeff Flake is stepping down from after one term in office. Both McSally and Sinema are letting go of their current seats in the House of Representatives for this fight. Whoever wins this race will make history as the first woman elected to the U.S. Senate from Arizona.
Polling has Heller and Rosen tied within the margin of error in the final stretch of this race. Heller was quoted as saying during the 2016 presidential election that he was “100 percent against Clinton, 99 percent against Trump.” That divide with the president has faded amid this tight race. Rosen, who represents Nevada's 3rd District in Congress, has former President Barack Obama's endorsement.
This is the most-watched senate race in the country. In what is normally a reliably red state, Cruz -- who finished second to Trump for the GOP presidential nomination 2016 -- has run into a buzzsaw. However, polls in recent days show Cruz is gaining distance. Some are hinting that O'Rourke could be the next Democratic superstar if he gets the win here. But O'Rourke told a CNN Town Hall on Oct. 18 that it is a "definitive no" on running for president before he completes his Senate term.
This is the seat being vacated by Senator Bob Corker. Blackburn is the U.S. representative from Tennessee's 7th district, while Bredesen is a former Tennessee governor. This race got a sudden pop from pop star Taylor Swift in early October via hear Instagram account. Swift made the rare move of diving into politics by publicly endorsing Bredesen and denouncing Blackburn.