Four Key Races Could Determine Fate of U.S. Senate Control 
 
 A lot more is happening on Election Day than just the race for president most notably, whether the Democrats will be able regain control of the Senate. Toomey and McGinty are basically deadlocked. Of the 10 seats Democrats are defending, none are in states that were won by either John McCain or Mitt Romney in 2008 or 2012. That may work near Philadelphia, where Hillary Clinton is crushing Donald Trump, but Trump is well-liked elsewhere. A CNN poll showed him with a 13-point edge in the past week. (Seth Perlman/AP) 
 
 Illinois 
 
 Sen. Mark Kirk (R) has used a wheelchair since he had a stroke in 2012, and against virtually any other opponent, his return to the Senate would be a powerful narrative on which to run. Clinton is favored to win the state by more than 10 percentage points, and no Republican has won a Senate race in Illinois in a presidential election cycle since 1972. But he is doing less so in the rural stretch between Philadelphia and Pittsburgh, in part, strategists say, because he hasn’t said whom he supports for president. Probable Democratic pickup 
 
 Wisconsin (86 percent) 
 
 Wisconsin may be closer than our forecast suggests: Our model may not have fully picked up a late shift in the polls toward incumbent Republican Sen. Ron Johnson. He raised more money than all but one Senate Republican (Patrick J. Toomey, who is in a close contest), and spent it early and often, a smart tactic in hindsight. Polls have shown a tight race for months, and although Burr has had a small lead in most recent polls, he has not been able to run far ahead of Donald Trump in a state where Democrats are making an extra-hard turnout push. And Cortez Masto’s is focused on Donald Trump, trying to energize Hispanics and mocking Heck’s wavering support for the GOP nominee. (Erik Verduzco/AP) 
 
 Nevada 
 
 Senate Minority Leader Harry M. Reid’s retirement announcement rocked Nevada’s political scene, creating the GOP’s only chance to capture a Democratic seat on the Senate battleground. (David Weigel/The Washington Post) 
 
 Missouri 
 
 Many Republican and Democratic operatives agree: No Senate challenger has run a better race than Jason Kander (D), Missouri’s secretary of state. It was a viral TV ad that had Kander assembling a military-style rifle with a blindfold that caught Washington’s eye, but it’s months of disciplined, pitch-perfect campaigning that puts him within a hair of unseating Roy Blunt (R) in a state likely to favor Donald Trump by double digits. The race pits Rep. Joe Heck (R), who represents the Las Vegas suburbs, against former state attorney general Catherine Cortez Masto (D), who would be the first Latina senator. Much of Heck’s campaign isn’t focused on his rival but instead on Reid — casting him as a villain who chose his puppet to succeed him. (Jim Cole/AP) 
 
 New Hampshire 
 
 For months, polls in New Hampshire have shown Sen. Kelly Ayotte (R) in a near dead heat with Gov. Although the race has tightened, Democrats and some Republicans think Feingold has an edge: Early voting has outpaced expectations in Democratic strongholds, and Johnson is only now showing signs of outpacing Donald Trump. Maggie Hassan a tossup again. After Duckworth described her family’s military heritage, Kirk said he had “forgotten that your parents came all the way from Thailand to serve George Washington.” Although Duckworth’s mother is a Thai immigrant, her late father’s lineage can be traced to the Revolution. On the presidential level, it has been within a few percentage points of the national vote in every election since 1996. The candidate who carries the independent vote in the state (which has one of the largest independent votes in the nation) will probably win the race. Plausible Democratic pickups 
 
 Indiana (40 percent), North Carolina (30 percent) 
 
 Democrats thought they hit the jackpot when they were able to recruit former Indiana Sen. Evan Bayh into the race to replace retiring Republican Sen. Dan Coats. Bayh entered the race with strong support from Democrats, who have fond memories of his time as governor and senator. He also had a giant fundraising war-chest and opened the race with a large lead over Republican Todd Young. The result is that Young took his first lead in a public poll in the last two weeks. His opponent is Deborah Ross, a lawyer and former state lawmaker whose record as a civil-rights advocate many assumed would be too liberal for the state. Ross has kept it close with Burr the entire campaign, but she’s never been able to overtake him. — Vanessa Williams 
 
 
 
 Rubio, right, and Murphy debate on Oct. 26 at Broward College in Davie, Fla. (Wilfredo Lee/AP) 
 
 Florida 
 
 The most important day in Florida’s Senate race was June 22, when GOP Sen. Marco Rubio announced that he would seek reelection — reversing a pledge he made when he began his ill-fated presidential campaign. Democrats, meanwhile, thought they had a winner in Rep. Patrick Murphy, a young up-and-comer who had triumphed in the nastiest and most expensive House race of 2012. Murphy, for his part, has been called out for exaggerations about his record and has attacked Rubio for supporting Trump, even after Rubio called Trump a con artist in the presidential primary. Rubio’s advantage is so large at this point that it’s difficult to imagine Murphy winning even if Clinton wins the state. (Ross D. Franklin/AP) 
 
 Arizona 
 
 Sen. John McCain (R) is poised to win a sixth term after a tough two-front battle with his state’s far-right wing and Democrats accusing him of flipping his positions to fit the moment. That set up a quick and potentially difficult general-election battle against Rep. Ann Kirkpatrick (D), who represents the state’s largest district. Meanwhile, Portman’s negative ads battered Ted Strickland, who began the race as a well-liked former governor. But McCain and Portman have been perhaps more successful than any other Republican Senate candidates in distancing themselves from Trump. Harris, 52, whose parents emigrated from Jamaica and India, would become the second black woman elected to the Senate since 1992. Summer polls showed Feingold with a double-digit lead, but the well-respected Marquette Law School Poll found last week that that margin had shrunk to a single point amid a late GOP ad blitz. The state will hold on a primary on Tuesday in which all the Democratic candidates and Republican candidates run against each other. As long as no candidate gets 50 percent (and there’s basically no chance of that happening), the two top vote getters regardless of party affiliation will advance to a runoff. State election rules allow the top two finishers, regardless of party, to advance to the general election. It is possible that one party will win most of the battleground races.
– So which party will control the Senate next year? Flip a coin. That's the current assessment at FiveThirtyEight.com, which gives Democrats a 52% or 53% chance of regaining control and a 16% chance of a 50-50 tie. In the latter case, the new VP would cast tie-breaking votes. Not too long ago, most forecasts comfortably predicted that Democrats would wrest control, but things have tightened considerably. The GOP currently has a 54-46 advantage (two independents caucus with Democrats), but Democrats have an opportunity to pick up ground up because 24 of the 34 seats up for grabs are held by Republicans. Some key races, per FiveThirtyEight, the Washington Post, and NBC News: New Hampshire: GOP Sen. Kelly Ayotte has been in a virtual dead heat with Democratic Gov. Maggie Hassan. This race in particular "is expected to play a critical role in determining which party will hold the Senate majority next year," notes the Post. Wisconsin: Republican Ron Johnson is defending his seat in a tight race against a familiar Democratic name, former Sen. Russ Feingold. Pennsylvania: Incumbent Republican Pat Toomey, a staunch conservative, is in a close one with challenger Katie McGinty, who could get a boost if Hillary Clinton wins the state. Illinois: GOP incumbent Mark Kirk is in real danger of losing to Democratic Rep. Tammy Duckworth. (Moments like this haven't helped him.) Missouri: Democratic challenger Jason Kander has a chance of ousting Republican incumbent Roy Blunt. Nevada: Harry Reid is retiring, and Republicans hope to get a flip of their own. The GOP's Joe Heck is keeping it close with Democrat Catherine Cortez Masto.