With Election Day nearly here, the battle for the Senate remains far from certain, with each side having a legitimate chance of improving its standing in the upper chamber.

Nearly all of the races that have been contested on the Senate map all election remain highly competitive, leading to a marked level of uncertainty as to which party will gain ground on Tuesday.

The most likely scenario appears to be no net change or a one-seat swing in either direction in the upper chamber after two years of clashes and hundreds of millions of dollars in ad spending. But with a number of races on the razor’s edge, strategists in both parties acknowledge that there’s still a real if remote chance Democrats could win the Senate — and that Republicans could still significantly expand their majority.

It’s unlikely but not impossible that Democrats can net the three seats necessary for Senate control, while Republicans’ early hopes for big gains in the upper chamber look unlikely as well. Avoiding losses would be a victory in itself for Democrats given how tough the Senate map is this year, with 10 Democrats up for re-election in states Trump won and just one GOP-held seat up in a state Trump lost.

The closing month of the race has made things harder for those red-state Democrats, as the debate over Supreme Court Justice Brett Kavanaugh’s confirmation and President Trump’s intense focus on fear-mongering over immigration and heavy travel schedule through the red states have helped galvanize Republican base voters.

But off-the-charts early voting numbers in nearly all of the competitive Senate races compared to those states in past midterms give Democrats hope that they can hang on in some tough races.

The only red-state Democratic senator of the 10 who looks cooked at this point is Sen. Heidi Heitkamp (D-ND), who has trailed Rep. Kevin Cramer (R-ND) in public and private polls for months. Strategists in both parties are counting that race in the GOP column.

Republicans and Democrats also agree that Missouri Attorney General Josh Hawley (R) has held a slight edge over Sen. Claire McCaskill (D-MO) in the race’s closing month. Hawley drew some bad headlines in the final week of the race that are giving Democrats some hopes McCaskill can hang on, but they don’t feel great about her standing.

Democrats are increasingly confident that they’re going to defeat Sen. Dean Heller (R-NV), however, as booming early vote totals indicate Heller is getting swamped in heavily Democratic Clark County — a view with which most Republicans agree.

In Arizona, brutally effective attack ads hitting Rep. Kyrsten Sinema (D-AZ) for her past statements mocking her state’s voters have helped Rep. Martha McSally (R-AZ) claw back into a close race in the election’s final weeks. Republicans think she’s pulled even and the race is a jump ball, but Democrats believe that Sinema has maintained a narrow lead based on their latest polling and early vote analysis.

The battle between Sen. Joe Donnelly (D-IN) and businessman Mike Braun (R) may be the closest and least predictable in the country. Democrats admit Donnelly’s lead was erased during the Kavanaugh fights and he was slightly trailing a few weeks ago, but they think he’s turned the corner. Republicans are split about where things stand — some believe the race is a pure tossup, others think Braun has opened up a lead — but most national strategists in both parties wouldn’t be surprised to see this race go either way.

Another very close race is in Florida, where private polling from both parties indicates a margin-of-error contest between Sen. Bill Nelson (D-FL) and Florida Gov. Rick Scott (R) rather than a slightly more comfortable lead for Nelson that’s been found in the public polls. Early vote turnout in the state also suggests a very close race between the two. Democrats feel more confident about this race than Republicans, but it’s not the sure thing some public polls have suggested.

Sen. Jon Tester (D-MT) has also seen his race against state Auditor Matt Rosendale (R) tighten in the final month, with the Kavanaugh fight and a heavy focus on the state by President Trump making his path to re-election harder. Strategists in both parties still think Tester is likely to hang on, but the race is much closer than conventional wisdom suggested just weeks ago.

Democrats also haven’t given up hope on flipping a pair of solidly Republican states, though both remain uphill battles. If everything else goes right, Democrats still need a win in one of these states for Senate control.

Democrats and some Republicans agree that the battle between Rep. Marsha Blackburn (R-TN) and Phil Bredesen (D) remains close. Quality private polling in this race has been all over the map, as both parties have seen numbers suggesting a tied race and other internal polls showing Blackburn with a lead. This race likely leans towards Blackburn — but plenty of Republicans remain very nervous that she may not hang on in the contest.

Texas looks like an even tougher lift for Democrats. Sen. Ted Cruz (R-TX) has maintained a lead outside the margin of error over Rep. Beto O’Rourke (D-TX) in nearly every public and private poll of the race. Booming early vote could scramble the models a bit, and Democrats are seeing a major surge in young voters in the state that makes them think O’Rourke could pull off a miracle upset. But Republicans roll their eyes at this, confident that Cruz will win.

A number of Democrats in states Trump won are sailing to reelection. Sens. Tammy Baldwin (D-WI), Sherrod Brown (D-OH), Bob Casey (D-PA) and Debbie Stabenow (D-MI) all are expected to win their races with ease, and while things have tightened up slightly in West Virginia, Sen. Joe Manchin (D-WV) remains the heavy favorite for victory.

Democrats have had to dump millions in last-minute spending to bail out scandal-plagued Sen. Bob Menendez (D-NJ) in a blue state and shore up recently appointed Sen. Tina Smith (D-MN). They think both will hang on with wins in the mid-single digits, but neither is a slam-dunk.