Senate Minority Leader Mitch McConnell's (R-Ky.) Democratic adversaries are shuddering at his retirement as GOP leader more than celebrating it.

Why it matters: McConnell is the bulwark of a dying breed of old-guard Republicans being systematically replaced with right-wing hardliners.

• "As frustrated as we have been with him at times, he — at moments — seemed committed to governing," Rep. Dan Kildee (D-Mich.) told Axios.
• "It can definitely get worse."

The backdrop: Once the head of a "legislative graveyard" for Democratic bills and nominees, McConnell has emerged as the symbol of a bygone Republican.

• His fraught relationship with former President Trump after Jan. 6 and his efforts to fund the government and pass aid to Ukraine have solidified an image of him as the leader of the GOP's pro-governance wing.

State of play: McConnell's successor is most likely to be one of the "Johns" — Sens. John Thune (R-S.D.), John Cornyn (R-Texas) or John Barrasso (R-Wyo.).

• Barrasso is friendlier with right-wingers, while Cornyn and Thune are more establishment figures.
• But all three have been more attuned than McConnell to the GOP's rightward lurch on issues such as infrastructure and foreign aid.
• Unlike McConnell, they all have endorsed Trump for reelection in 2024.

What they're saying: Rep. Haley Stevens (D-Mich.) said Democrats are "more concerned about a replacement than what we got from McConnell over and over again."

• "From the Supreme Court to gun laws to January 6th, could it really get much worse? I shudder to think it could," she said.
• "I'm no Mitch McConnell fan, but his replacement could be a lot worse," Sen. Elizabeth Warren (D-Mass.) said.
• Former House Majority Leader Steny Hoyer (D-Md.) said McConnell "cared about the institution and ... stability" and that he's "not confident he's going to be replaced by someone who mirrors those core instincts."

Between the lines: Even Democrats who have clashed bitterly with McConnell emphasized his ability to work across the aisle in their statements on Wednesday.

• "While we often disagreed, we shared our responsibility to the American people to find common ground whenever possible," said former House Speaker Nancy Pelosi (D-Calif.).
• Senate Majority Leader Chuck Schumer (D-Calif.) said they "rarely saw eye to eye" but "came together in the last few years to lead the Senate forward at critical moments."

The other side: For some Democratic lawmakers, McConnell's legacy —  particularly with regard to the federal judiciary — cannot be forgiven.

• "McConnell was responsible for the Supreme Court we have right now, so I'm not a huge fan of his record," said Rep. Jim McGovern (D-Mass.).
• "He represents the niceties of the past, but ... the stuff he has advanced I think has been very damaging to the country."

Zoom out: Looming large over the race to succeed McConnell is Trump, whose influence over GOP senators is likely to be a big factor.

• "Anybody who is closer to Donald Trump is going to be a problem," Sen. Dick Durbin (D-Ill.) told Axios. "I hope … a more moderate person emerges."
• "My hope is that when [McConnell] steps down in November, Trump will have been rejected at the ballot box," said Rep. Wiley Nickel (D-N.C.).

Editor's note: This article has been updated with comment from Former House Majority Leader Steny Hoyer.