Reminding his party one more time exactly how much power he yields in a split chamber, Sen. Joe Manchin delivered another blow to a potential progressive agenda under President Joe Biden amid renewed — but only brief — optimism that the moderate West Virginia lawmaker could be open to dumping the time-honored Senate filibuster.

A procedural tool that offers immense power to the minority, the filibuster requires a 60-vote threshold to advance legislation, effectively ensuring — given the current 50-50 Senate — that Republicans would have the power to prevent Democrats from enacting sweeping policy changes under Biden. (No party has held 60 seats in the Senate since Democrats briefly did after Barack Obama's election in 2008.)

Manchin, the Senate's leading proponent of preserving the filibuster, expressed openness over the weekend to slightly reforming it, such as reinstating the "talking filibuster." That would require that senators physically remain on the chamber floor to block legislation. Currently, members can simply inform leadership they plan to filibuster without being present.

Effectively, a talking filibuster would create a higher bar for the minority to block bills and might mean that the Senate majority could simply play a sort of waiting game. For a fleeting moment, progressives thought that perhaps Manchin was coming around, only to have their hopes squashed on Tuesday when he clarified his position. In the Senate's 50-50 split, Democrats would need every single one of their members to be on board in order to vote the filibuster into oblivion.

"I want to make it very clear to everybody: There's no way that I would vote to prevent the minority from having input into the process in the Senate," Manchin told Politico. "That means protecting the filibuster. It must be a process to get to that 60-vote threshold."

Manchin will undoubtedly face increased pressure the deeper we go into the Biden administration, since it's abundantly clear Senate Republicans will block any number of the president's initiatives. Moderates like Manchin say the remedy is found in bipartisanship and negotiation. Progressives say it's long past time to trash the filibuster, which is not enshrined in the Constitution and certainly wasn't contemplated by the founding fathers.

But Manchin isn't alone; Sen. Kyrsten Sinema is right there with him. The Arizona Democrat is also against removing the filibuster. Unlike Manchin, the lone elected statewide Democrat in what is now a red stronghold, Sinema represents a state that has been trending increasingly blue for some time. Biden narrowly carried Arizona, and the state now has two Democratic senators. (Sen. Mark Kelly, who ousted GOP incumbent Martha McSally in November, is the other.)

The Grand Canyon State's voters are apparently more interested in passing new laws than preserving abstruse Senate rules, or so recent polling suggests. AData for Progress surveyreported by Vox showed that 61 percent of voters indicated they favored passing significant legislation, while just 26 percent said they preferred to "preserve traditional Senate procedures and rules like the filibuster."

In a recent letter to a constituent, Sinema noted the long-term consequences dumping the filibuster could have on a future Democratic minority.

"Regardless of the party in control of the Senate, respecting the opinions of senators from the minority party will result in better, common-sense legislation," Sinema wrote. "My position remains exactly the same now that I serve in the majority. While eliminating the filibuster may result in some short-term legislative gains, it would deepen partisan divisions and sacrifice the long-term health of our government."

A slew of Republican senators have thrown in the towel. At least five GOP incumbents are planning not to run for re-election next year, making way for a potential seismic ideological shift in the upper chamber.

With most of the outgoing lawmakers considered to be old school, pragmatic conservatives, their GOP colleagues say the institution may be adrift without their leadership.

This exodus may offer Democrats increased optimism that they may be able to hold onto a Senate, despite the long tradition that the sitting president's party typically loses seats in midterm elections. But on the other side of the aisle, it remains to be seen what path the Republican Party chooses to go down: Does it back candidates who align themselves with Donald Trump, or those who try to distance themselves from him?

The writing is on the wall, argues GOP strategist Susan Del Percio, citing the retaliatory measures numerous state Republican parties have taken against members of their party who voted to impeach Trump. But Del Percio sees danger here: Shifting further to the Trumpian right would further undermine the possibility of substantive policy debate and open the door for more Democratic wins, she said.

"It's the latest casualty of what Trump has done to the Republican Party," Del Percio told Salon. "State committees are Trump-controlled. You'll see people go more and more to the right in who they nominate and support. It doesn't mean they'll win the seat."

On Monday, Sen. Roy Blunt of Missouri became the fifth GOP senator to reveal that he will not seek re-election next year, joining a list of departing colleagues that has swelled in recent months.

Blunt's revelation meant that one-tenth of the Senate Republican Conference is leaving, a startling statistic that could continue to grow; Ron Johnson of Wisconsin and Chuck Grassley of Iowa have not yet announced their plans for 2022. (Grassley, now in his seventh term, will turn 88 just before the next midterm election.) Zero Senate Democrats have said they plan to retire.

"After 14 general election victories — three to county office, seven to the United States House of Representatives and four statewide elections — I won't be a candidate for re-election to the United States Senate next year," Blunt said in avideo statement posted to social media. He did not cite a specific reason for his decision to step aside.

A leadership member who often immersed himself in detailed policy negotiations as an institutionalist and conservative lawmaker, the 71-year-old has now joined Richard Burr of North Carolina, Pat Toomey of Pennsylvania, Richard Shelby of Alabama and Rob Portman of Ohio on the list of Republican retirees.

"It seems that in recent times, it's all about beating the other person or preventing them from winning, not about putting forward good, sound policies," Del Percio said. "These are more than just political people like Josh Hawley and Ted Cruz. They cared about what they were doing, and about moving policies forward. It is devastating."

Most of the departing senators are on the older side, although Toomey is just 59 — relatively young, for the Senate — and they're all younger than Grassley. This flight of conservatives from federal public office is more likely a byproduct of the fatigue among sitting Republicans created under the Trump era, which saw the traditional, conservative wing of the party diminished, if not conclusively defeated.

Blunt's retirement caused at least one election forecaster to shift the Missouri race one rating to the left, from "Safe R" to "Likely R." It's hard to imagine states as red as Missouri or Alabama ever going for a Democrat. Then again, Alabama's 2017 special election, in which Democrat Doug Jones triumphed over Republican Roy Moore, who was accused of repeated acts of sexual misconduct with underage girls, proved it's possible against the right candidate. In states like Pennsylvania, North Carolina and Ohio, open-seat Senate races are likely to be competitive, and candidates hewing too closely to the Trump mold could alienate all-important suburban voters and galvanize Democratic turnout.

Praise for Blunt from his current and former colleagues came immediately, mirroring that for his fellow retiring Republicans. Lawmakers and aides who had the pleasure of crossing paths with Blunt agreed the Senate is losing a valuable policy wonk, who is generally well liked on both sides of the aisle. Both Senate Minority Leader Mitch McConnell, R-Ky., and Sen. John Cornyn, R-Texas, described his retirement as a "big loss" for the upper chamber. In a statement, McConnell called Blunt "a true leader, a policy heavyweight and a driving force behind both key conservative victories and essential bipartisan work." Whether his departure offers an unexpected opening for Democrats or another pathway for Donald Trump's total conquest of the Republican Party, it's too early to say.

A watchdog group has demanded that Sen. Lindsey Graham, R-S.C., a close ally of Donald Trump, be removed from the Senate Judiciary Committee over his attempt to pressure a Georgia election official to reverse the former president's stunning loss in the Peach State.

The Checks and Balances Project (CBP), a nonpartisan investigative group, has written to Senate Minority Leader Mitch McConnell requesting that Graham immediately relinquish his position on the prestigious Judiciary Committee, which oversees the nomination of federal judges, including Supreme Court justices.

"My question to you is this," CBP executive director Scott Peterson wrote to McConnell, in a letter sent Monday night that was provided to Salon. "Is it appropriate for a Senator to serve on the Senate Judiciary Committee when he is under investigation for such a serious crime?"

The Atlanta Journal-Constitution reported last month that the district attorney Fulton County, Georgia, was probing whether Graham had broken any state election laws when the South Carolina Republican phoned Georgia Secretary of State Brad Raffensperger in the days after the November election. Graham, according to Raffensperger, urged him to toss out legal absentee ballots to shrink Trump's deficit.

Graham has long denied the allegation, saying that he was simply inquiring about the signature-matching process during the Georgia recount then underway. But Peterson feels the investigation is grounds for McConnell to remove Graham from the powerful Judiciary panel — which he chaired under the previous Congress — at least until the criminal inquiry is concluded.

"Someone who engages in that type of activity doesn't belong on the U.S. Senate Judiciary Committee," Peterson told Salon. "In this country, every vote counts. The right to vote is the backbone of our democracy. And instead of fighting for the Constitution and democracy, Sen. Graham called … Raffensperger to try to get him to throw away votes and rig the election."

A spokesperson for Graham noted that this was CBP's second effort to target him, the first being earlier this year when the group wanted lawmakers to push Attorney General-designate Merrick Garland to commit to investigating both Graham and Trump. McConnell's office did not respond to Salon's request for comment.

When the allegations about the Raffensperger phone call first emerged in November, Graham called the assertions that he tried to alter the election's outcome "ridiculous." Raffensperger rebuffed Graham's alleged guidance, but had he followed it and disqualified ballots that had been legally cast by mail, Raffensperger, who is also a Republican, would himself have committed election fraud.

"What I'm trying to find out was, how do you verify signatures on mail-in ballots in these states that are just the center of attention?" Graham told reporters in November, while attempting to justify the content and context of the Raffensperger call.

Graham's alleged involvement, which was first disclosed in aRaffensperger interview with The Washington Post, is reportedly part of a broader criminal probe by Fulton County D.A. Fani Willis into whether then-President Trump broke any laws by pushing Raffensperger to "find" enough votes to win him the state.

"I urge you to ask Senator Graham to step down from the Judiciary Committee until all investigations into his conduct in Georgia are complete," Peterson wrote to McConnell. "If we are to restore public faith in our democracy, this step will go a long way to re-establishing the idea that no one is above the law."