(CNN) Secretary of State Mike Pompeo's decision not to run for the open Senate seat in Kansas this November is a major blow to Republicans hoping to avoid a competitive race in one of the most GOP-friendly states in the country.

2020 Senate election map

Had Pompeo, who represented the state's 4th district from 2010 to 2016, run, he would have walked to the Republican nomination and been a heavy favorite to replace retiring Sen. Pat Roberts (R) in the fall. Without him, there is now the very real possibility that former Kansas secretary of state Kris Kobach winds up as the GOP Senate nominee -- a prospect that could imperil the seat for Republicans.

Kobach is a deeply divisive figure within the Kansas Republican Party -- and the state more broadly. He made a national name for himself by championing hardline immigration policies that won him the praise and attention of President Donald Trump. Early in his presidency, Trump named Kobach as the chair of a commission to examine alleged voter fraud in the country, although the commission was disbanded after less than a year.

Kobach then embarked on a run for governor in 2018, narrowly ousting the appointed governor in a Republican primary before losing in the general election to Democrat Laura Kelly. (Trump endorsed Kobach in his contested primary fight, calling him "a fantastic guy who loves his State and our Country.") Following that loss, Kobach was reportedly considered to be Trump's immigration czar, but was eventually passed over -- perhaps due to a wild list of reported demands he had for taking the job.

So when Kobach announced last year that he planned to seek the seat vacated by Roberts, the reaction among many Republicans was, uh, not friendly.

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