(CNN) Sen. David Perdue, a Georgia Republican up for reelection and a close Trump confidant, issued a blunt warning to GOP activists during an off-the-record conference call this week: Democrats are in position to turn his state blue and take the Senate.

"Here's the reality: The state of Georgia is in play," Perdue said Monday, according to an audio recording of a call with "Women for Trump" obtained by CNN. "The Democrats have made it that way."

The stark warning from a GOP senator -- who is not considered among the most vulnerable Republicans this election cycle -- illustrates the fear among Republicans that Democrats' chances of taking back the Senate continue to grow.

Already facing the prospect of defending the Senate with an unpopular Republican president in an election cycle with more seats to defend than to target, Republicans are up against a bevy of well-funded Democratic challengers and are now navigating a public health and economic crisis that has injected deep uncertainty into the national political landscape.

Indeed, the political environment for GOP senators has only become more challenging in the past few months. Republican incumbents in Colorado, Arizona, Maine and North Carolina always knew they would face a tough path to reelection. Now Republicans in more conservative states -- Georgia, Iowa, Montana and even Kansas -- have realized the same.

Republicans are particularly concerned that the intraparty battles in Kansas and Georgia, two states Trump carried in 2016, could make it easier for Democrats to gain the three seats they need to take back the Senate if former Vice President Joe Biden wins the presidency since the vice president breaks a 50-50 tie.

Behind the scenes, GOP senators are trying to instill fear into their base and mobilize their loyal voters into action, Republican sources say. On the private Monday call, Perdue told the GOP activists that the 2020 elections would be a "turning point for America."

'Our wake-up call in Georgia'

The Georgia senator laid out an apocalyptic view in the eyes of Republicans if Democrats take back the Senate, warning they would seek to make Washington, DC, and Puerto Rico states, try to abolish the Electoral College, add four justices to the Supreme Court and create a "single-party system."

"We have had our wake-up call in Georgia," Perdue said, detailing the state's recent electoral history of increasingly tight races. Perdue said he needs to win "twice the number of votes" than he did in his 2014 campaign to keep his seat due to the influx of new Democrats in Georgia. "The demographic moves against us. But we can still win this if we get out and make sure that all of our voters vote. That's what this comes down to."

Ginger Howard, a Georgia committeewoman for the Republican Party, responded that Perdue's analysis was "very sobering."

"It's hard to hear," she said on the call. "The truth hurts sometimes -- and we need to know that because we've got to work doubly hard."

Asked for comment about the call, Perdue spokeswoman Casey Black said: "From day one, our campaign has known that this will be a competitive race. With his strong record of proven results in the US Senate, we are confident that Georgia voters will re-elect David Perdue this November." Howard didn't respond to an inquiry seeking comment.

Perdue's assessment is striking in part because both parties view his race as less competitive than the other Senate race in Georgia, a special election to fill the seat of the retired Sen. Johnny Isakson. In that race, candidates of all parties will be on the ballot in November -- and whoever takes a majority of the vote will win the seat outright; otherwise there will be a runoff between the top two candidates.

With Loeffler and Collins engaged in a ferocious and personal fight, Republican leaders are worried that it will only boost the chances of Reverend Raphael Warnock, the senior pastor of the Ebenezer Baptist Church in Atlanta and a Democrat who raised $1.5 million in the first quarter.

The Rev. Raphael G. Warnock speaks during the Martin Luther King, Jr. annual commemorative service in January at Ebenezer Baptist Church in Atlanta.

In a recent interview, Warnock attacked Loeffler, who has faced questions over stock trades in her portfolio made before the market took a nosedive , the subject of a new pro-Collins super PAC ad.

"Right now, Georgia has a senator, who when she received the news about the coronavirus pandemic, seemed to be more focused on sheltering her own investments than she was in making sure that those who were sheltering in have the protections that they need," said Warnock.

Stephen Lawson, a spokesman for Loeffler, disputed Warnock's allegation, saying she has put "people -- not politics --first" during the coronavirus crisis.

"While Mr. Warnock is parroting baseless accusations from the radical left, Sen. Loeffler is working around the clock to deliver relief to Georgians impacted by Covid-19," Lawson said.

Presidential influence

Republicans in Washington are worried that their incumbent senators are not getting the recognition they deserve for backing emergency rescue legislation to prop up the faltering economy, including hundreds of billions of dollars for small businesses, hospitals, workers and the unemployed. Instead, their governors are generally receiving the lion's share of the credit for implementing the states' response.

What's more: Republicans need Trump to steady his handling of the pandemic, given that many of their electoral prospects will depend on his performance at the polls

Whit Ayres, a prominent GOP pollster, said it will be a "challenge for Republican senators to run very far ahead of the President" given the deeply polarized electorate.

"That means the President's standing in each of these states is every bit as important or more important than the senator's standing," Ayres said.

On the private call, Perdue made clear his affinity for Trump and gushed about the President's handling of the crisis.

"I really think that President Trump is a person of destiny," Perdue said when asked how Trump's response to the pandemic "helped save lives."

Several Democrats, including former congressional candidate Jon Ossoff, 2018 lieutenant governor nominee Sarah Riggs Amico and former Columbus mayor Teresa Tomlinson, are vying for the chance to take on Perdue. But the Republican senator boasts a huge fundraising advantage with over $9 million on hand and an easier path to reelection than at least seven other GOP incumbents, according to political handicappers.

Looking at Kansas and the rest of the country

But the challenges for Republicans extend well outside of that race. In the first quarter of the year, Republicans in seven other Senate races -- in Arizona, Maine, North Carolina, Colorado, Kansas, Georgia and Montana -- were outraised by Democratic challengers

In Kansas, a state which has not elected a Democrat to the Senate since 1932, Democratic state Sen. Barbara Bollier raised nearly $2.4 million, much more than any of her potential Republican challengers, in the first quarter of the year. The race has become one of the biggest headaches for Republicans, in large part because of the divisive primary.

State GOP chair Mike Kuckelman has urged two candidates to drop out of the race, which could give Rep. Roger Marshall a better chance to defeat Kobach and plumbing-business owner Bob Hamilton, whose late entrance has upended the race.

"As we've said for months, this is a two-man race," said Eric Pahls, Marshall's campaign manager. "The last thing Kobach wants is a one-on-one race with Dr. Marshall. While we can't control what others do, we can keep working harder than anyone and focusing on what has worked for us: talking with Kansans about what matters to them."

Danedri Herbert, Kobach's spokeswoman said that Hamilton's entry into the race "probably helps" their campaign. "Now moderate Republicans have two people to choose from -- Hamilton and Roger Marshall," she said.

A person with knowledge of Hamilton's plans said that Kobach's failure to win in the governor's race in 2018, coupled with conservatives who are actively fighting Marshall's candidacy, gives the businessman the best chance to win. Hamilton has the resources to partially fund his own campaign.

"Our candidacy puts a lot of fears to rest if he's the nominee," the source said.

President Donald Trump waves after speaking alongside then-Kansas Secretary of State Kris Kobach in the Eisenhower Executive Office Building next to the White House in July 2017.

Republican leaders in Washington don't want to spend money in Kansas, but fear they may have to if the race appears to be slipping away.

On Tuesday, the Democratic Senatorial Campaign Committee announced it would reserve more than $30 million in fall advertising for four states Trump won in 2016: Arizona, North Carolina, Iowa and Montana. Republicans have two offensive opportunities -- in deep red Alabama and Michigan, where Sen. Gary Peters was outraised by challenger John James last quarter.

But the money race so far has benefited the Democrats. And even in those where it hasn't, like in Iowa -- a state Trump won by over nine points in 2016 -- outside groups have made sure to keep it competitive. Two rival super PACs -- the Senate Leadership Fund and Senate Majority PAC -- have announced they'd set aside over $25 million dollars to advertise this fall in Iowa.

The National Republican Senatorial Committee has realized the threat of losing the Senate, reserving ads starting in June, earlier than the past cycle, with at least $31 million reserved for the cycle in seven states, an amount that is certain to grow. The Senate Leadership Fund, which is aligned with Senate Majority Leader Mitch McConnell, has already reserved $67 million in six key states, more than double its initial amount in 2018. It already has spent roughly $2 million against Collins in Georgia.

Senate Majority PAC, which is aligned with Senate Democratic Leader Chuck Schumer, has likewise reserved over $69 million in fall advertising time.

"We do have a competitive situation in the Senate," McConnell said on Wednesday, noting on Fox News radio that 23 Republican and only a dozen Democrats are up for reelection. "So yes, we're on defense—and we've got competitive races all over the place."