(NewsNation)  — The 2024 presidential election is still anybody’s game, but polling suggests Democrats are facing an uphill battle to maintain control of the U.S. Senate.

Republicans have to win just one of two competitive races in red states — Montana or Ohio — to secure a surefire majority, assuming everything else goes as projected.

NewsNation’s election partner, Decision Desk HQ, shows Republicans with a 71% chance of winning the Senate as of Oct. 31.

Scott Tranter, the director of data science at DDHQ, recently explained what goes into that projection: “We have over 20,000 polls in our database from this cycle, as well as past performance and voter registration [data].”

Other variables, like fundraising amounts, also go into the model, Tranter said.

In this election, GOP candidates are favored to flip blue seats in Montana, Ohio and West Virginia. Two other Democratic incumbents — Senator Tammy Baldwin from Wisconsin and Senator Bob Casey from Pennsylvania — are in closely contested races.

Meanwhile, Democrats will try to pull off upsets in Missouri and Texas, hoping to unseat two prominent GOP senators — Ted Cruz and Josh Hawley — both of whom are in closer races than they’d prefer.

Here are the current odds in 13 key Senate races.

Arizona: Kari Lake vs. Rep. Ruben Gallego

In this combination photo, Kari Lake speaks in Dallas, Aug. 5, 2022, left, and Rep. Ruben Gallego, D-Ariz., is seen in the Capitol, July 14, 2022, in Washington. (AP Photo)

Chance of winning, according to Decision Desk HQ (as of Oct. 31):

Gallego (D): 82%

Lake (R): 18%

Decision Desk HQ polling averages (as of Oct. 31):

Gallego (D): 49.7%

Lake (R): 43.5%

What to know: Trump-backed former TV anchor Kari Lake is eyeing an Arizona Senate seat after coming up short in her 2022 bid for governor, but polling suggests she has a tough hill to climb.

As recently as July, Lake and U.S. Rep Ruben Gallego, D-Ariz., were within three points of each other, but since then, Gallego has widened the margin to more than six points. He’s also raised considerably more money: over $56 million versus Lake’s $21 million.

Florida: Sen. Rick Scott vs. Debbie Mucarsel-Powell

Sen. Rick Scott (R-Fla.), left, and former Rep. Debbie Mucarsel-Powell (D-Fla.) are in a tight race for Florida’s Senate seat.

Chance of winning, according to Decision Desk HQ (as of Oct. 31):

Scott (R): 75%

Mucarsel-Powell (D): 25%

Decision Desk HQ polling averages (as of Oct. 31):

Scott (R): 49.5%

Mucarsel-Powell (D): 44.8%

What to know: Once a hotly contested swing state, Florida now leans Republican. That bodes well for GOP Senator Rick Scott, the incumbent, who won by a slim 10,000 vote margin in 2018.

Democratic challenger Debbie Mucarsel-Powell, a former representative from Miami, will have to overcome a roughly 5-point polling gap and a $10 million spending disadvantage to flip the seat blue.

Maryland: Larry Hogan vs. Angela Alsobrooks

On the left, candidate for Maryland Senate Angela Alsobrooks speaks during day two of the 2024 Democratic National Convention in Chicago on Tuesday, August 20, 2024. (Bill Clark/CQ-Roll Call, Inc via Getty Images). On the right, Former Maryland governor and and Republican Senate candidate Larry Hogan speaks during a campaign event at the VFW Post 9619 in Morningside, Maryland. (Photo by Nathan Howard/Getty Images)

Chance of winning, according to Decision Desk HQ (as of Oct. 31):

Alsobrooks (D): 99%

Hogan (R): 1%

Decision Desk HQ polling averages (as of Oct. 31):

Alsobrooks (D): 53.8%

Hogan (R): 41.0%

What to know: In August, an AARP poll showed Democrat Angela Alsobrooks and former GOP Governor Larry Hogan in a dead heat, but the race hasn’t been particularly close since then. Maryland hasn’t had a Republican U.S. senator since 1987.

Michigan: Rep. Elissa Slotkin vs. Mike Rogers

This combination photo of Michigan Senate candidates shows Rep. Elissa Slotkin, D-Mich., in Detroit, Aug. 6, 2024, left, and former Rep. Mike Rogers, R-Mich., Aug. 6, 2024, in Lake Orion, Mich. (AP Photo)

Chance of winning, according to Decision Desk HQ (as of Oct. 31):

Slotkin (D): 67%

Rogers (R): 33%

Decision Desk HQ polling averages (as of Oct. 31):

Slotkin (D): 48.1%

Rogers (R): 45.1%

What to know: U.S. Rep Elissa Slotkin, D-Mich., has outspent her GOP opponent, former Rep. Mike Rogers, by more than 5 to 1, yet the race remains tight. Rogers has narrowed the polling gap in recent weeks, but Slotkin still holds a three-point advantage, according to Decision Desk HQ.

Missouri: Sen. Josh Hawley vs. Lucas Kunce

Republican Sen. Josh Hawley and Democrat Lucas Kunce engaged in an impromptu showdown at the Missouri State Fair. The candidates have been fighting over a potential debate. (Kacen Bayless/The Kansas City Star/Tribune News Service via Getty Images)

Chance of winning, according to Decision Desk HQ (as of Oct. 31):

Hawley (R): 89%

Kunce (D): 11%

Decision Desk HQ polling averages (as of Oct. 31):

Hawley (R): 51.5%

Kunce (D): 45.2%

What to know: Republican incumbent Josh Hawley has become one of the more recognizable figures on the new American right, but attorney Lucas Kunce, a Marine veteran, is trying to change that. To do so, Kunce will have to dramatically defy expectations in a state that backed Donald Trump by more than 15 points in 2020.

The two are set to debate on Thursday, Oct. 31, hosted by NewsNation local affiliate KTVI in St. Louis. The debate is scheduled to begin at 7 p.m. CT.

Montana: Sen. Jon Tester vs. Tim Sheehy

Republican challenger Tim Sheehy, left, and Sen. Jon Tester (D-Mont.).

Chance of winning, according to Decision Desk HQ (as of Oct. 31):

Sheehy (R): 74%

Tester (D): 26%

Decision Desk HQ polling averages (as of Oct. 31):

Sheehy (R): 50.0%

Tester (D): 45.2%

What to know: Senator Jon Tester, the incumbent, is the most vulnerable Democrat this cycle and is now considered an underdog against GOP challenger Tim Sheehy. The reason is fairly straightforward: Montana is a solidly red state that Trump won by more than 16 points in 2020.

“[Tester’s] reputation as a straight-shooting, authentic, and deeply rooted rural Montanan arguably matters less than ever in a highly nationalized electoral environment and in a Montana that has changed dramatically since his last run in 2018,” Kal Munis, a political scientist and Montana native, wrote in a recent Brookings article.

Nevada: Sen. Jacky Rosen vs. Sam Brown

US Senate candidate Sam Brown, left, and Sen. Jacky Rosen (D-Nev.)

Chance of winning, according to Decision Desk HQ (as of Oct. 31):

Rosen (D): 80%

Brown (R): 20%

Decision Desk HQ polling averages (as of Oct. 31):

Rosen (D): 48.9%

Brown (R): 43.3%

What to watch: Republican presidential candidates have been gaining ground in Nevada in recent elections, so much so that it has become a legitimate swing state. But losing by less and winning are two different things.

Republican Adam Laxalt came up short in his 2022 Senate bid, losing to Democrat Catherine Cortez Masto. Now, polling suggests Democratic incumbent Jacky Rosen is heavily favored to retain her seat against Republican challenger Sam Brown.

New Mexico: Nella Domenici vs. Sen. Martin Heinrich

Democratic Senator Martin Heinrich (left) and Republican challenger Nella Domenici (right)

Chance of winning, according to Decision Desk HQ (as of Oct. 31):

Heinrich (D): 94%

Domenici (R): 6%

Decision Desk HQ polling averages (as of Oct. 31):

Heinrich (D): 50.5%

Domenici (R): 39.2%

What to watch: Democratic incumbent Martin Heinrich has raised more than twice as much as GOP challenger Nella Domenici, the daughter of the last New Mexico Republican elected to the Senate.

Domenici will have to pull off a major upset to get elected in a state that Joe Biden carried by more than 10 points in 2020.

Ohio: Sen. Sherrod Brown vs. Bernie Moreno

This combination photo shows Sen. Sherrod Brown, D-Ohio, Oct. 26, 2023, on Capitol Hill in Washington, left, and Cleveland businessman Bernie Moreno, a Republican candidate for Senate, in Westlake, Ohio, March 19, 2024. (AP Photo)

Chance of winning, according to Decision Desk HQ (as of Oct. 31):

Moreno (R): 54%

Brown (D): 46%

Decision Desk HQ polling averages (as of Oct. 31):

Moreno (R): 47.7%

Brown (D): 46.9%

What to know: Polls suggest Democratic incumbent Sherrod Brown could be in trouble against Republican businessman Bernie Moreno. A few elections ago, Ohio was a key battleground state, but since then, it’s grown increasingly red.

“There’s been several polls over the last week that have [Moreno] anywhere from one to three points ahead, on top of the fact it looks like Donald Trump’s going to probably win the state by five to seven points,” Tranter told NewsNation’s Markie Martin on Monday.

Pennsylvania: Sen. Bob Casey vs. David McCormick

This combination of photos taken in Pennsylvania shows Sen. Bob Casey, D-Pa., left, at a campaign event, Sept. 13, 2024, in Wilkes-Barre, and David McCormick, the Republican nominee for Senate in Pennsylvania, at a campaign event, April 25, 2024, in Harrisburg. (AP Photo)

Chance of winning, according to Decision Desk HQ (as of Oct. 31):

Casey (D): 72%

McCormick (R): 28%

Decision Desk HQ polling averages (as of Oct. 31):

Casey (D): 48.0%

McCormick (R): 45.5%

What to know: Businessman David McCormick is back after narrowly losing to Dr. Mehmet Oz in the Republican primary election for the Senate back in 2022. McCormick was trailing by about seven points in early September but has since cut Democratic incumbent Bob Casey’s lead to less than three points.

Casey’s war chest is almost twice as big, and he’s outraised McCormick $52 million to $27 million.

Texas: Sen. Ted Cruz vs. Rep. Colin Allred

(AP Photo/Mariam Zuhaib, File/J. Scott Applewhite)

Chance of winning, according to Decision Desk HQ (as of Oct. 31):

Cruz (R): 75%

Allred (D): 25%

Decision Desk HQ polling averages (as of Oct. 31):

Cruz (R): 49.1%

Allred (D): 45.9%

What to watch: Former presidential hopeful and current Senator Ted Cruz is facing a tough battle for his seat in the Lone Star State. If Democratic challenger Rep. Colin Allred can pull it off, it would be a major upset. Current polls suggest that’s unlikely, though not impossible.

“Ted Cruz won his last race by 2.6% against Beto O’Rourke six years ago, and right now, he’s polling better than that,” Tranter said.

West Virginia: Jim Justice vs. Glenn Elliott

West Virginia Gov. Jim Justice and Glenn Elliott are facing off for the Senate seat in West Virginia.

Chance of winning, according to Decision Desk HQ (as of Oct. 31):

Justice (R): >99%

Elliott (D): <1%

What to know: Republicans are all but guaranteed to pick up outgoing Senator Joe Manchin’s seat. Trump carried the state by roughly 30 points in 2020, meaning the Senate candidate with “R” by their name has a pretty good shot.

That means West Virginia GOP Governor Jim Justice is likely headed to the U.S. Senate. He’s outspent his Democratic opponent, Glenn Elliott, by 5 to 1.

Wisconsin: Eric Hovde vs. Sen. Tammy Baldwin

Sen. Tammy Baldwin, left, (D-Wis.) speaks before President Biden at the Earth Rider Brewery Jan. 25, 2024, in Superior, Wis. Eric Hovde, right, a Republican businessman and real estate mogul announces he is for running U.S. Senate against incumbent Baldwin, Feb. 20, 2024, in Madison, Wis.

Chance of winning, according to Decision Desk HQ (as of Oct. 31):

Baldwin (D): 63%

Hovde (R): 37%

Decision Desk HQ polling averages (as of Oct. 31):

Baldwin (D): 48.2%

Hovde (R): 47.7%

What to know: Wisconsin is another state where anything could happen. Democratic incumbent Tammy Baldwin has a major fundraising advantage but just narrowly leads in the polls. GOP challenger Eric Hovde, a businessman, currently has the momentum.

At the start of October, Hovde was behind by more than four points; now, that gap is less than half a point, according to Decision Desk HQ.