With just 28 days before Americans head to the voting booth, numerous incumbent Republican senators are struggling to keep pace with their Democratic challengers in public polling and in fundraising.
And as a result, leading election forecasters see it increasingly likely that a number of them may lose their seats.
It's the latest sign that Senate Majority Leader Mitch McConnell could lose control of the upper chamber, which the Kentucky Republican has led since January 2015.
"I think it's 50-50," McConnell told conservative radio host Hugh Hewitt on Friday about the prospects of keeping the Senate majority. "We always knew this was going to be a challenging cycle. We have close, hard-fought races all over the country. The Democrats are competing with us in Kansas, Georgia and even South Carolina. The American people have a big decision to make."
With a 47-member caucus, Democrats need a net gain of at least three seats, so long as they also win the presidency so that a Democratic vice president could break any ties. There are currently 53 Republicans. But Republicans have 23 seats up for re-election compared to Democrats' 12.
Eight seats held by Republicans are listed as "toss-ups" or "lean Democrat" by Cook Political Report. Six of them are in states won by President Donald Trump. Just one Democratic seat, held by Sen. Doug Jones (Ala.), is rated "lean Republican."
Moreover, races in GOP strongholds like Kansas, Georgia and South Carolina—as mentioned by McConnell—have become increasingly in play for Democrats.
And despite hopes and predictions among Senate Republicans that the fight to confirm a new conservative Supreme Court justice before Election Day would buoy their chances of maintaining the majority, the partisan debate has only driven more cash into the pockets of Democratic challengers.
"Senate Republicans enter the final weeks of this election pouring millions of dollars into states they never expected would be competitive, and are still struggling to explain their indefensible records of voting to eliminate protections for pre-existing conditions and their failed coronavirus response," Democratic Senatorial Campaign Committee spokesperson Stewart Boss said in a statement. "Four weeks from now, Americans across the country are going to vote for change and elect a Democratic majority in the Senate."
What the polls, fundraising and election forecasts are saying
Arizona
Sen. Martha McSally (R) is projected to lose her re-election fight to Democrat Mark Kelly, a former astronaut. Cook Political Report rates the race as "lean Democrat." FiveThirtyEight predicts there is a 79 percent chance Kelly wins.
Kelly's average lead over McSally in the polls is +6.6 points, according to Real Clear Politics, which is down from his all-time high of +11.3 a month ago but up from +5.2 last week. Five polls published in the past week show McSally down by anywhere from 4 to 13 points.
Kelly has dominated McSally in fundraising, eclipsing her in total money raised by nearly $16 million. As of mid-July, Kelly had raised $46.1 million and had $21.2 million cash on hand, per Federal Election Commission filings. McSally raised $30.4 million as of September 8 and had $10.9 million in the bank.
Colorado
Sen. Cory Gardner (R) is also projected by Cook to lose against Democratic Gov. John Hickenlooper. Cook has the race as "lean Democrat." FiveThirtyEight gives Hickenlooper a 75 percent chance of winning, up from 65 percent on September 2.
Four polls in the last two months show Hickenlooper outpacing Gardner by anywhere from 5 to 10 points. Hickenlooper's lead in polls over the past year have averaged at +10.3 over Gardner.
In fundraising, Gardner maintained a slight advantage going into the third quarter. The incumbent raised $17.2 million and had $10.7 million in the bank as of July 24. Hickenlooper raised $14.2 million and had $4.6 million cash on hand as of June 30.
But in the third quarter, Hickenlooper raised $22.6 million and had $7.2 million in the bank going into October.
Maine
Cook rates the match between Sen. Susan Collins (R) and Democratic challenger Sara Gideon, speaker of the Maine House of Representatives, as a "toss-up." FiveThirtyEight has increased the likelihood Gideon unseats Collins from 51 percent on September 16 to 62 percent as of Tuesday.
Gideon has maintained an edge in the polls on Collins that averages +6.5 points. Eight polls in the past month show the two candidates anywhere from tied to Gideon leading by 12 points.
Collins continues to trail Gideon in fundraising. Gideon raised $24.2 million and had $5.4 million cash on hand as of June 30. Collins raised $16.9 million and had $5.6 cash reserves as of September 30.
North Carolina
The race between Sen. Thom Tillis (R) and Democratic challenger Cal Cunningham is rated as a "toss-up" by Cook. FiveThirtyEight awards Cunningham a 66 percent chance of winning.
Cunningham has an average lead over Tillis in recent polls by 6.5 points, up from his 3.3-point lead in mid-September. In the past month, 23 polls show Tillis trailing Cunningham from 1 to 13 points.
Cunningham has a slight edge in fundraising. He raised $15.1 million and had $6.6 million in the bank as of June 30. Tillis raised $14.3 million and had $6.9 million cash on hand for the same time period.
New third quarter fundraising numbers released by Cunningham's campaign show the Democrat hauled in $28.3 million in the past three months.
Cunningham has suddenly found himself immersed in controversary. The Democrat admitted over the weekend to sending sexual messages to a women who is not his wife. He's since apologized and rebuffed calls from Republicans to drop out.
Iowa
Another "toss-up" race by Cook, FiveThirtyEight shows Sen. Joni Ernst (R) and Democratic challenger Theresa Greenfield virtually tied. Last month, they predicted Ernst with a 59 percent chance of winning but have since decreased it to 51 percent.
Greenfield has an average lead of five points in the polls. Seven surveys over the past month show anywhere from Ernst leading by five to Greenfield ahead by 12.
Ernst is still outraising her challenger. The incumbent brought in $14.6 million as of June 30 and had $9.1 million in the bank. Greenfield raised $11.6 million and had $5.7 million in reserves as of June 30.
Georgia
Also a "toss-up" race for Cook, Sen. David Perdue (R) is projected by FiveThirtyEight as having a 73 percent chance at holding onto his seat over Democrat Jon Ossoff.
Perdue has an average 2.8-point lead over Ossoff in recent polls. In 13 surveys in the past month, the results have fluctuated from Perdue leading by as much as eight points to Ossoff ahead by five points.
Perdue also leads in fundraising. He's brought in $14.9 million and had $10.7 million cash on hand as of September 30. Ossoff raised just $7.3 million and had $2.5 million in the bank for the same time period.
Montana
Cook lists the face-off between Sen. Steve Daines (R) and Montana Gov. Steve Bullock, a Democrat, as a "toss-up." FiveThirtyEight gives Daines a 65 percent chance of winning re-election.
Two polls in the past month have Daines slightly leading Bullock by one and three points.
Fundraising figures have been equally as close. Daines raised $13 million and had $7.1 million cash reserves as of June 30. Bullock brought in $11.2 million and had $7.6 million in the bank.
South Carolina
Cook shifted their rating for the match-up with Sen. Lindsey Graham (R) and Democrat Jaime Harrison from "lean Republican" to "toss-up" on Wednesday. FiveThirtyEight awards Graham a 79 percent of winning, down slightly from a high of 87 percent on September 13.
Half a dozen surveys in the past month show the candidates within the margin of error, ranging from Graham ahead by one point to Harrison leading by two points.
The two are also near neck-in-neck in fundraising. Graham has brought in $30.9 million and had $15 million cash on hand as of June 30. Harrison raised $29 million and had $10.2 million in the bank.
Harrison has seen an influx of donations in recent months amid narrow polling, which the current FEC filings do not account for.
Kansas
With Sen. Pat Roberts (R) retiring, Cook has the showdown between Republican Roger Marshall and Democrat Barbara Bollier as "lean Republican." FiveThirtyEight gives Marshall a 79 percent chance of winning.
Four polls in the past month show the race ranging from Bollier ahead by two points to Marshall leading by seven points.
But Bollier has a sizable cash advantage. She's raised $7.8 million and had $4.2 million cash on hand as of July 15. Marshall brought in just $2.7 million and had $1 million in the bank as of September 8.
Georgia
The special election for incumbent Sen. Kelly Loeffler (R), who was appointed to fill the seat of Sen. Johnny Isakson (R), who retired in December 2019 for health reasons, has been marred by intra-party fighting.
Rep. Doug Collins (R-Ga.), an ardent supporter of Trump and who helped lead the public battle against the president's impeachment with his powerful position on the House Judiciary Committee, is challenging Loeffler. The two GOP candidates are splitting the Republican electorate, making it all the more likely that a run-off election will be needed because of the open primary format where candidates from both parties all run at the same time.
Still, Cook rates the seat as "lean Republican." The National Republican Senatorial Committee has attacked Collins for mounting his challenge and urged him to drop out. Trump has not endorsed either candidate.
Polls indicate that Loeffler and Democrat Raphael Warnock are likely to face each other in a one-on-one run-off. A Quinnipiac University survey last week showed Warnock ahead of both Republicans for the first time.
Loeffler was far outpacing either candidate in fundraising. As of June 30, she'd outraised Warnock and Collins each by roughly 4:1.
However, the gap could dwindle. The Warnock campaign has said it raked in nearly $13 million in the third quarter.
This story was updated to note that the South Carolina Senate race was shifted to a "toss-up" by Cook Political Report and to include new fundraising numbers for Hickenlooper.
