Florida Rep. Vern Buchanan announced Tuesday that he will be retiring from Congress after 20 years in office, the latest Republican to forgo seeking reelection amid a challenging midterm environment for the party.

Buchanan, who represents the red 16th District that includes some of Tampa’s suburbs along the Gulf Coast, is a longtime member of the House Ways and Means Committee.

“Serving the people of Southwest Florida has been the honor of my lifetime,” Buchanan said in a statement. “After 20 years of service, I believe it’s the right time to pass the torch and begin a new chapter in my life.”

First elected in 2006, Buchanan became a key player on tax, trade and health care policy.

Washington is charging toward a partial government shutdown over President Donald Trump’s immigration enforcement agenda even as senators and the White House scramble to find an elusive off-ramp.

Democrats, Republicans and the White House each say they want to avoid another costly lapse in government funding. But Saturday’s killing of a 37-year-old Minnesota man by federal agents has badly complicated the approach pattern for a massive six-bill appropriations package that the Senate planned to approve this week.

In the wake of the Minnesota shooting, Democrats want Republicans to join them in stripping out funding for the Department of Homeland Security from the sprawling package. Yet any changes would require further action in the House, which is out of town until Monday — after a shutdown would start at 12:01 a.m. Saturday.

Republicans are dangling alternatives that would avoid having to change the massive bill, including potential executive actions or an agreement to pass a separate piece of legislation. But Democrats believe they have leverage as Americans recoil at Trump’s aggressive immigration enforcement tactics in Minnesota and elsewhere.

The captured-on-video killing of Alex Pretti has sparked public unease even from Trump allies in Congress and fueled new questions about how the administration is enacting its agenda, putting intense pressure on Democrats to dig in and fight.

Senate Minority Leader Chuck Schumer said Monday that the “responsibility to prevent a partial government shutdown” lies in the hands of Majority Leader John Thune and his fellow Senate Republicans. He called on them to agree to strip out and renegotiate the DHS bill while allowing the rest of the package — which would fund nearly three-quarters of annual agency spending — to be passed into law.

As recently as Friday, enough senators were expected to help pass the full set of funding bills, which was negotiated over the course of months by bipartisan appropriators. Now, according to a person granted anonymity to disclose private discussions, Democrats are quickly “coalescing” around a number of changes they want to the DHS bill, which won only seven Democratic votes in the House.

Those include requiring judicial warrants for immigration arrests, overruling a recently disclosed ICE memo asserting they are not required. Other potential Democratic amendments would mandate federal agents identify themselves, require DHS to cooperate with state and local investigations and limit the “mission creep of federal agencies.”

Despite the concern that has emerged within the GOP ranks after Saturday’s shooting, Republicans are moving forward with the six-bill package as currently drafted, taking a first step Monday to put it on the floor. Senators are expected to take an initial vote Thursday, when at least eight Democrats will be needed to leap a 60-vote hurdle.

Senate Appropriations Chair Susan Collins (R-Maine) told reporters Monday that she did not favor removing the DHS bill from the six-bill package but that there are ongoing discussions about “further reforms or procedural protections.”

“My hope is that we’re not going to get to that point, that everyone would recognize that a government shutdown is extremely harmful and should be avoided,” Collins said when asked about the prospects for a partial shutdown.

Sen. Katie Britt (R-Ala.), who leads the Appropriations subcommittee dealing with DHS and met with Collins Monday, also told reporters the Senate should pass the funding package as is but that there could be actions taken “within the purview of the administration” to address Democrats’ concerns.

Some lawmakers and aides held out hope that some of Trump’s moves Monday, which included sending border czar Tom Homan to oversee the Minnesota enforcement surge, would soften the ground for a possible deal. Others were encouraged that lines of communications remained open between the parties early in the week.

Republicans are facing their own internal pressures as they seek to avoid a shutdown. A group of conservatives, including Sen. Mike Lee (R-Utah), is vowing to oppose any effort to strip out DHS funding. And because the Senate is locked in a time crunch with the Friday midnight deadline looming, any one senator can block an attempt to quickly amend the legislation.

At the same time, there are some Democratic qualms about pushing agencies to the brink less than three months after ending a record 43-day shutdown fought over health care. Some are noting that ICE and Border Patrol will continue to be funded in any case through the GOP megabill enacted last year while other DHS agencies such as FEMA and TSA would be subject to the shutdown.

But so far Democrats are insisting that Republicans agree to rewrite the bill. Democrats are skeptical that the administration can be trusted to take executive action or that standalone legislation reining in DHS would ever make it through the House.

“My options are to do nothing or to recognize that two U.S. citizens were recently … executed by federal agents,” Sen. Ruben Gallego (D-Ariz.) told reporters Monday. “We need to at least bring some level of pressure on DHS or on our Republican colleagues to explain to the American public why we are going to continue funding this without any changes.”

Even sending an amended bill back to the House would carry the risk of an extended standoff. One senior House Republican granted anonymity said that would open a new “hellscape” in the funding talks, with the fractious GOP conference divided over the way forward.

“Democrats already had a say in DHS funding during the bipartisan negotiations that occurred on each and every individual appropriations bill,” said a House GOP aide granted anonymity to speak candidly about the dynamics. “If they renege on the agreement on any of these bipartisan bills, then it would open a bigger can of worms.”

Privately, many Republicans on Capitol Hill believe that any off-ramp to be found before Friday night’s deadline will need to come from the White House, according to two people granted anonymity to disclose private thinking.

But the administration said Monday it wants to see the six-bill package passed as written — without the DHS funding separated out.

“Policy discussions on immigration in Minnesota are happening,” White House press secretary Karoline Leavitt said, adding that those talks “should not be at the expense of government funding for the American people.”

Speaker Mike Johnson’s leadership circle is still weighing options as the partial shutdown looms. While some Senate Democrats are calling on the House to cut its one-week break short and reconvene, there are no plans to bring the chamber back early, according to three people granted anonymity to comment on private planning.

While GOP leaders plan for now to bring the House back next Monday as scheduled, some rank-and-file Republicans are wary that Johnson might re-run his strategy from the last shutdown and keep the House out even longer in a bid to jam the Senate.

GOP Sen. Susan Collins said she spoke Monday to embattled Homeland Security Secretary Kristi Noem after the administration launched an immigration enforcement campaign in her home state.

Collins declined to divulge details of her conversation with Noem to reporters — though her office indicated earlier this month that the senator had reached out to DHS about ICE’s activities in Maine.

Regarding the ICE presence there, Collins said in a statement last week that “people who are in this country legally should not be targets of ICE investigations,” while those who have “entered this country illegally and who have engaged in criminal activity …. could be subject to arrest and deportation.”

She added, “People who are exercising the right to peacefully gather and protest their government should be careful not to interfere with law enforcement efforts while doing so.

But the conversation comes at a critical moment. Federal agents shot and killed a U.S. citizen in Minneapolis over the weekend, prompting public outrage and sparking criticism from a growing number of Senate Republicans about the Trump administration’s handling of the situation. It’s the second such shooting to occur in the city since January began.

Collins is also the chair of the Senate Appropriations Committee who helped negotiate legislation to fund several agencies — including DHS — through the end of September. That bipartisan package is now imperiled as Democrats now say they won’t vote to support any bill that funds DHS without significant guardrails in place to rein in immigration enforcement activities.

DHS is among several agencies that would shut down after Jan. 30 unless lawmakers can reach some sort of compromise.