(CNN)Republican Sen. Rob Portman's retirement announcement caught Washington DC by surprise. Portman, who won reelection in Ohio in 2016 by 21 points, was seemingly not on anyone's radar for potential retirement.
This is bad news for Republicans. Not merely because defending an open seat is more difficult than when an incumbent, especially a popular one like Portman, is running for reelection, but also because the departure of smart conservative workhorses like Portman leaves extreme candidates more likely to win a primary.
If they win, the party is changed for the worse. And if they lose, those extreme candidates still tend to define how the Republican Party is perceived.
That perception reflects a longtime trend.
2010 was a great year for Republicans. They gained more than 60 seats in the US House of Representatives and six US Senate seats. But two congressional candidates, both unsuccessful, planted the seed that Republican candidates were increasingly outlandish in their performance and beliefs. That seed grew.
In Delaware, Christine O'Donnell, a Tea Party-backed Republican Senate candidate, was forced to go on the defensive in an effort to explain her earlier remarks about "dabbl[ing] into witchcraft." Instead of focusing her attacks on her opponent, Democrat Chris Coons, she was running an infamous ad that began, "I am not a witch."
Meanwhile, in Nevada, Tea Party-supported Sharron Angle emerged from a crowded GOP field only to have her campaign against a potentially beatable Democrat, Harry Reid, sidetracked with her strange claims that some American cities were governed by sharia law (Islamic religious law) and her avoidance of the press -- in part, because of her odd statements.
In 2012, Missouri Republican Senate candidate Todd Akin, a candidate running against the vulnerable Democrat, Claire McCaskill, found himself on the defensive over comments about women's bodies supposedly blocking pregnancy after what he called "legitimate rape." Akin apologized, but later unapologized, and McCaskill won the election by some 15 points.
Akin practically had an ideological soulmate in Indiana's GOP Senate nominee, Richard Mourdock, who, in addition to questioning the constitutionality of Medicare and Social Security -- popular programs among seniors, the most reliable of voting blocs -- also made controversial comments about abortion. Specifically, he said God "intended" rape pregnancies. Though Mourdock later apologized for the "misinterpretation" of his comments, the damage was done. In another blown opportunity for Republicans, Democrat Joe Donnelly won election.
What these candidates all have in common is not simply costing the GOP winnable US Senate seats. It's that they began to define the party in the run up to former President Donald Trump's rise.
In 2010, O'Donnell became a household name and laughingstock. In 2012, Republican candidates throughout the country were taken off their messages as Democrats effectively nationalized the Akin and Mourdock comments, causing Republicans yet more problems with women voters.
While these candidates shared a willingness to stoke anger and use fiery rhetoric, they did not have Trump's command of media or ability to dominate the political conversation.
Which brings us back to the Portman retirement. Along with Portman, Sens. Richard Burr and Pat Toomey are retiring in North Carolina and Pennsylvania, respectively. And Arizona Gov. Doug Ducey says he won't run for US Senate in 2022.
It's possible Republicans might nominate Trump loyalists Rep. Jim Jordan to replace Portman and Lara Trump, Trump's daughter-in-law, to replace Burr. Meanwhile, the Arizona Republican Party Chair Kelli Ward, another Trump supporter, may run in the US Senate race in Arizona, in which Democrat Mark Kelly will be up for reelection. Not to mention that Trump's former press secretary, Sarah Sanders, announced Monday she was running for governor of Arkansas -- and received the former president's endorsement shortly after.
Win or lose -- and, to be clear, Ward, who has already lost two Republican primaries, could certainly lose again -- these candidates would further define the GOP as the party of Trump even as the former president's popularity has dropped following the insurrection he inspired. For the Republicans who hoped to put Trump in rear view mirror, this could spell disaster.
State parties may not care. Indeed, by attacking fellow Republicans, party officials in places like Arizona, Oregon and Virginia scare away potential moderate Republican voters who do not subscribe to Trumpism. Through censure and resolutions, these officials seek to cast out any Republican they view as not sufficiently loyal to the former President.
This was misguided enough during the Trump years. Traditionally, parties have believed it is important to grow their base -- not shrink it through loyalty tests. But as the GOP continues to go further down the road of tribalism, mistaking Trumpian tactics and controversy for long-term strategy, they risk further electoral and policy losses.