US midterm elections: Key races to watch

Congressional races, Senate races, gubernatorial races, it's all happening tomorrow. Here's some of the more interesting election battles to follow, and a few of the coin tosses that could turn the tide.

The midterms are really three different things happening simultaneously. There's a vote for Senate seats, a vote for congressional representatives, and a governor race all happening at once on Wednesday. Congressional representatives serve two-year terms which means all 435 seats are up for re-election. Senators serve six-year terms and 35 are up for grabs on Wednesday. There are governor's races in 36 states.

READ MORE: Making sense of the midterm election madness

Both houses of congress are currently controlled by Republicans. If Democrats gain control of the House of Representatives (which they look poised to do) they could hamper President Donald Trump and the GOP's policies on things such as tax cuts and the Obamacare repeal. They could also force more congressional oversight into alleged election fraud and sexual harassment claims. However, it won't make impeachment proceedings much easier because they requires two thirds of a senate vote.

It's very likely Republicans will keep control of Senate. Thirty-five seats are up for grabs, but most of them are Democrat seats. Democrats will need to keep all their seats while gaining two from the Republicans to gain control.

Data-driven analytics website FiveThirtyEight has the chances of Democrats taking the Senate at 18.9 percent as of writing.

Democrats, however, are predicted to make major gains in Congress. FiveThirtyEight has the chances of a Democrat win at 87.7 percent as of writing.

If Democrats gain control of both houses, Trump's administration is in big trouble. All law-making and policy would be essential controlled by democrats, though Trump would retain a veto power. Knowing his temperament, this would be a pretty interesting scenario. It would also mean Trump and the GOP would lose decision-making power in installing Supreme Court justices.

Key races to watch:

Senate:

Ted Cruz (R) vs Beto O'Rouke (D) for Texas Senate: Texas is a dependable red state, but Cruz has lost a lot of face after embracing Trump who humiliated him in defeat and insulted him and his family. If Beto won the senate vote, this would be a huge embarrassment to Cruz, Trump and the GOP. It would also be a bit wild for traditionally conservative Texan politics - he is pro-choice and expressed admiration for Colin Kaepernick.

Heidi Heitkamp (D) vs Kevin Cramer (R) for North Dakota Senate: Incumbent Democrat Heitkamp looks likely to lose her senate seat to the republican challenger. There are accusations of voter suppression here, with a law recently passed which requires voters to be registered to a residential address. Many Native Americans who live on reservations don't have a residential address, instead they have post boxes which don't count under the new law. The Native American vote helped get Heitkamp into her last election, so there will be questions raised if she fails this time around.

Claire McCaskill (D) vs Josh Hawley (R) for Missouri Senate: Hawley is a Republican challenger to two-term Democrat Claire McCaskill, whose support has been wavering in the face of Missouri Democrats making some strange decisions to bolster its support base, such as welcoming pro-lifers into the party. McCaskill has run a pretty weird campaign - one of her radio ads says she's not "one of those crazy Democrats".

Martha McSally (R) vs Kyrsten Sinema (D) for Arizona Senate: Jeff Flake, the current Republican senator and vocal critic of Trump is resigning with McSally ready to take the reins. Sinema, the Democrat challenger, is only marginally ahead in polls so it could be a close one.

Governor:

Stacey Abrams (D) vs Brian Kemp (R) for Georgia: Democrat Adams would be the first black woman to serve as a state governor if she won, and winning that in the South would be a watershed moment historically. Her opponent Kemp is a hardline Trump supporter who brandished a shotgun in his election ad and said he drives a big truck in case he needs to round up illegal immigrants. If Abrams loses this race, expect to see a lot of commentary on voter suppression in Georgia. There's been some dodgy stuff going down.

Andrew Gillum (D) vs Ron DeSantis (R) for Florida: This is probably the race that has caused the most controversy in the lead-up to the midterms. DeSantis, a Republican, told Florida voters not to "monkey this up" on television (Gillum is a black man). Gillum responded in a debate by saying "I'm not calling Mr DeSantis a racist, I'm simply saying the racists consider him a racist", which was a pretty great response. On Monday Trump's agriculture secretary Sonny Perdue said "this election is so cotton-pickin' important to the state of Florida" which is another example of race-baiting (cotton-picking having been plantation work for slaves). Gillum has also accused DeSantis of speaking at racist conferences and said he took, and refused to return, a donation from someone who referred to Obama as a Muslim n-word.

Shawn Moody (R) vs Janet Mills (D) for Maine: Mills, the Democrat challenger, is the attorney general of Maine. She's up against Moody who is taking over for Paul LePage, the current Governor. Moody calls himself a "lifelong common-sense conservative" who's made millions in business. However, the race is more about LePage than Moody. The current Governor is openly racist and said illegal immigrants of Hispanic origins and people of colour are "the enemy right now". Mills has a decent polling lead in this race, with a recent poll putting her eight points ahead.

Scott Walker (R) vs Tony Evers (D) for Wisconsin: Republican Walker has name recognition and two terms under his belt but the race is a toss up. Evers has had support from Bernie Sanders, Obama and Joe Biden in a final push to get him over the line.

House of Representatives:

Katie Hill (D) vs Steve Knight (R) for California 25th: Knight is the incumbent republican being challenged by 30-year-old Katie Hill who, despite swearing off Super PAC donations, has raised more money than Knight. She's been endorsed by President Obama and actor Kristen Bell.

Mimi Walters (R) vs Katie Porter (D) for California 24th: Incumbent republican Walters faces a strong challenge from democrat Porter after supporting the tax bill and the repeal of Obamacare which was unpopular in her district. This one is being labelled a toss-up but a recent NY Times poll had Porter slightly ahead.

Kevin Yoder (R) vs Sharice Davids (D) for Kansas's Third: Republican Yoder has voted on Trump lines and looks to lose this seat to Davids who would be among the first Native American women in Congress (Deb Haaland is set to take a seat on the day too). Davids is also openly LGBTQ.

Will Hurd (R) vs Gina Ortiz-Jones (D) for Texas' 23rd: Republic incumbent Hurd is on his second term. He's one of the most outspoken republican congressmen, having decried Trump's family separation policy and his meeting with Vladimir Putin. Democrat Ortiz-Jones is behind in the polls, but 23rd is a swing district that went for Clinton. Ortiz-Jones would be the first Iraq War veteran, Filipino, woman, and LGBTQ person to represent the district if elected.

Dana Rohrabacher (R) vs Harley Rouda (D) for California's 48th: Republican Rohrabacher is basically Putin's best mate and is openly joked about even by other fellow Republicans for his strong ties to Russia. His challenger, the Democrat Rouda, was until very recently a Republican and donor to the GOP. Rouda is polling just slightly ahead of Rohrabacher.

RNZ will be live-blogging results and reactions from midday on Wednesday.

- RNZ/ABC/BBC