This is not the way Republicans wanted to begin the year.

Missouri's Roy Blunt on Monday became the fifth Republican senator to announce he will not seek reelection, a retirement wave that portends an ugly campaign season next year and gives Democrats fresh hope in preserving their razor-thin Senate majority.

History suggests Republicans are still well-positioned to reclaim at least one chamber of Congress next year. But officials in both parties agree that the surge of GOP departures will make the Republicans' challenge more difficult in the Senate.

“Any time you lose an incumbent, it’s bad news,” said Republican strategist Rick Tyler, who briefly worked for failed Missouri Senate candidate Todd Akin nearly a decade ago. “Missouri’s not necessarily a safe state for Republicans. Democrats have won there.”

The 71-year-old Blunt's exit is a reminder of how the nation's politics have shifted since the rise of Donald Trump. Blunt and his retiring GOP colleagues from Ohio, Pennsylvania, North Carolina and Alabama represent an old guard who fought for conservative policies but sometimes resisted the deeply personal attacks and uneven governance that dominated the Trump era.

Their departures will leave a void likely to be filled by a new generation of Republicans more willing to embrace Trumpism — or by Democrats.

Several Missouri Republicans are expected to seek the nomination to replace Blunt, but none will be more divisive than former Gov. Eric Greitens, who resigned in 2018 amid the fallout of a sex scandal and ethics investigation. Missouri's Republican base has since rallied behind him, believing he was unfairly prosecuted.

Greitens was considering running for the GOP nomination even before Blunt's announcement. He is expected to announce his candidacy as soon as Tuesday morning.

Two leading Missouri Democrats, former Sen. Claire McCaskill and 2016 Senate candidate Jason Kander, both said they would not run for the open seat.

Ahead of Greitens' announcement, some Republicans worried that he could jeopardize the Senate seat if he emerges as the party's nominee.

Steven Law, a key ally of Senate Minority Leader Mitch McConnell and CEO of the Senate Leadership Fund, warned that Republicans may be beginning to repeat the mistakes of 2010, when the GOP lost the Senate majority by embracing flawed far-right candidates.

“We have an opportunity to win back a majority,” Law said. “But in 2010, that opportunity was lost on the Senate side because of unelectable candidates who got nominated.”

Back in 2010, tea party favorite Christine O’Donnell beat a longtime GOP congressman in the Delaware Senate primary before losing by a landslide in the general election following reports of personal financial difficulties, questionable use of campaign funds and allegations that she had “dabbled into witchcraft.”

Two years later in Indiana, Richard Mourdock defeated six-term Sen. Richard Lugar in the 2012 GOP primary, but he imploded after a debate in which he said pregnancy resulting from rape “is something that God intended.” In Missouri, Republican nominee Akin lost after he insisted on a local talk show that women’s bodies have ways to avoid pregnancy in cases of “legitimate rape.”

In the decade since Akin's debacle, Missouri's politics, like the nation's, have evolved in a way that gives both parties opportunities.

States like Missouri, Ohio and Iowa, recently considered swing states, are trending away from Democrats. At the same time, previous red states like North Carolina and Georgia are trending away from Republicans.

Missouri hasn't elected a Democratic senator since McCaskill beat Akin in 2012. Trump carried the state last November by 15 percentage points. Trump carried Ohio, where Republican Sen. Rob Portman will not seek reelection next year, by 8 percentage points. The former president won by the same margin in Iowa, where 87-year-old Republican Sen. Chuck Grassley is considering retirement.

Democrats are expected to be more competitive in North Carolina, where Trump eked out a victory by just 1 percentage point, and in Wisconsin, should Republican Sen. Ron Johnson follow through with a campaign promise not to seek more than two terms.

Democrats have not lost any incumbents to retirement, but they are defending vulnerable incumbents in Georgia and Arizona, among others.

They have no margin for error. Republicans will claim the Senate majority for the last two years of President Joe Biden's term if they pick up even one additional seat next November.

The party that occupies the White House traditionally suffers significant losses in the first midterm election of a new president. President Barack Obama's Democratic Party, for example, lost 63 seats in the House and six in the Senate in 2010.

Democrats are hopeful that Trump will become an unwitting ally in 2022. The former Republican president has vowed to play an active role in the midterms, particularly by supporting pro-Trump candidates in primary elections. That leaves little room for well-established Republicans like Blunt who are popular statewide.

"The challenge for Republicans will be the race to the bottom in the Republican primaries," said Morgan Jackson, a leading Democratic strategist based in North Carolina. “It’s not about what you say, it’s about how loud and angry you say it. That’s a very different view of the world.”

Jackson said “it's a safe bet” Republicans will win the House majority, but he's optimistic that Trump's meddling in Senate primaries will help limit Democrats' losses.

“Maybe it won’t be a good cycle, but maybe it won’t be a bad cycle,” he said.

J.B. Poersch, who leads the Democratic-allied Senate Majority PAC, noted that Republicans are focused on the nation's culture wars, while Democrats are in the process of sending billions of dollars to working-class Americans affected by the pandemic. That contrast will help Democrats, he said.

“There is a working-family economic argument that Democrats can still make in the middle of the country, in places like Missouri and Ohio, and keep them competitive,” he said.

Meanwhile, Blunt predicted political success for Republicans in Missouri and beyond during a Monday news conference. He also reflected upon the 2010 election, when Democrats were punished nationwide after embracing Obama's fiscal stimulus and health care overhaul.

“I think 2022 will be a great year in the country and I think it will be a fine year in this Senate race,” Blunt told reporters. “The Republican Party will be just fine.”