When Sen. Bob Corker (R-Tenn.), once mocked by President Donald Trump as “Liddle’ Bob Corker,” retired in 2018, Trump loyalist Marsha Blackburn succeeded him. When Sen. Jeff Flake (R-Ariz.) retired, he gave a farewell speech making clear that he didn’t want to be “complicit” in the Trump agenda but declined to defend his seat in a primary. On Monday, Sen. Rob Portman (R-Ohio) announced that he, too, would not seek another term, noting, “We live in an increasingly polarized country where members of both parties are being pushed further to the right and further to the left.”

On one level, it’s easy to sympathize: It’s almost impossible to be a traditional Republican in the Trump era. And to be a senator of any stripe in a divided Senate can seem pointless. Portman wasn’t wrong to point out that “it has gotten harder and harder to break through the partisan gridlock and make progress on substantive policy.”

But by pulling the plug rather than facing a potentially bruising primary (or a tightly contested general election) — and risking a rout at the polls — these senators all evaded the bigger debate about the future of the Republican Party: Instead of taking a stand to help the GOP revert to a right-of-center, problem-solving party that doesn’t see compromise as a dirty word, they’re standing aside while the party remakes itself as a xenophobic cult of personality for conspiracy theorists and trade protectionists. Fear of defeat is handing their party over to Trump, his loyalists and Trumpism — and it is warping the country.

As former president Donald Trump’s second impeachment trial nears, lawmakers discussed on Jan. 31 whether he should be held accountable for the Capitol breach. (The Washington Post)

Portman is an instructive example. He worked for Presidents George H.W. Bush and George W. Bush, including as Bush 43’s U.S. trade representative and Office of Management and Budget director. He served for more than a decade in the House of Representatives, where he toiled closely with liberal Rep. Ben Cardin (D-Md.) on pension reform. Portman has favored free trade and containing deficits.

But in the Senate, he has often opted for partisan strategy over actual lawmaking. Republican Leader Mitch McConnell (Ky.) named him in 2011 as one of three Senate Republicans on the Gang of 12, a bicameral working group tasked with addressing the deficit by either trading Social Security and Medicare cuts for tax increases, or else triggering mindless and destructive across-the-board budget cuts. There, he blocked the responsible path, because it would have meant a tax hike.

Throughout Barack Obama’s presidency, when McConnell used the filibuster to sink an array of Obama nominees (including his last Supreme Court pick, Judge Merrick Garland) and various legislative proposals, Portman went along, even reversing course on issues he would have previously supported: After backing international trade deals throughout his career, he came out against the Obama-negotiated Trans-Pacific Partnership. Despite his 2016 election-year opposition to Garland’s nomination, Portman voted to confirm Judge Amy Coney Barrett to the high court in 2020. He was a part of the gridlock that he now decries. He didn’t vote for Trump in 2016 but eventually acquiesced to the president’s style and program. On the budget-busting tax cuts that Trump urged and that passed in 2017, Portman, a long-standing champion of balanced budgets, voted in favor. He opposed witnesses and voted to acquit Trump in the first impeachment trial.

The story isn’t that much different for other Republicans in the Senate who aren’t closely tied to Trump. Sen. Pat Toomey (Pa.), who has also announced his retirement, voted against Trump’s national emergency declaration aimed at funding his border wall. Toomey urged swift action on the pandemic relief bill Congress passed in December — which Trump stalled before eventually signing — telling Fox News, “Let’s get this into law,” then haggle over $600 vs. $2,000 direct payments. But he was more often a Trump and McConnell loyalist. Corker challenged Trump on relations with Russia, saying Trump’s Helsinki news conference with President Vladimir Putin made the United States look like a “pushover.” He said he wished he hadn’t backed Trump in 2016. But when it came time for reelection, he bowed out.

It’s true that even before Trump’s ascendancy in late 2015, the Republican Party had become, as Thomas Mann and I wrote, “ideologically extreme; scornful of compromise; unmoved by conventional understanding of facts, evidence and science; and dismissive of the legitimacy of its political opposition.” But it still offered at least lip service to small-government, free-market ideas, as well as support for immigration and a pro-democracy foreign policy. Those notions needed defenders, and now they have few on the right.

Trump was aided by right-wing media and the zealotry of his core supporters, who lapped up his macho, revanchist shtick and attacks on his and their perceived enemies more than any genuine expression of conservative ideology. But he also benefited greatly as major figures within his party failed to offer a different vision or act to counter his destructive behavior.

Now, when someone like Portman says he’s packing it in, what he’s really saying is that he doesn’t want to go toe-to-toe with a primary challenger. He’s not interested in selling the idea that the GOP should break with Trump.

The result of capitulation is predictable: The Republican Party is increasingly captured by the extremism of the Trump strain, which is unwilling to make any sort of accommodation with Democrats — even obvious moderates such as Obama and President Biden. Legislating becomes impossible, which fuels extremists’ charge that the system should be overturned rather than overhauled. The failure of Flake, Portman, Corker and others to seek anything but a sure-shot reelection enables a self-perpetuating cycle. Members of Congress leave for lots of reasons, including the lure of the private sector, but it’s hard not to think that Portman and others departed partly because they wouldn’t fight for the kind of comity, moderation and principle they claim to yearn for.

Contrast their exits with the pending fate of Rep. Adam Kinzinger (R-Ill.), an increasingly outspoken critic of Trump who has already drawn a 2022 primary challenger but says, “Leaders have got to start telling the truth.” Our democracy cannot last for long without two parties that compete on the basis of programs and ideas.

Flake and Corker are out of the fray. Portman and Toomey will soon be. They do have two years to make the case for reasonable conservative plans for pandemic relief, infrastructure, climate, health care coverage, trade, economic inequality and even democracy reform. There may not be much of an audience for that conservative case. But if they don’t even try to make it — if they use their pending retirements to check out for the rest of their terms — Trump’s forces will own the GOP for a long time to come. And that would be tragic for our country.

Twitter: @NormOrnstein