Astronaut Mark Kelly, who is running as a Democrat to take the late John McCain's former U.S. Senate seat in Arizona, was snubbed by fellow astronauts last week.

What is the background?

Kelly is running against Sen. Martha McSally (R-Ariz.) in a close race to take control of the seat that was left vacant by McCain's death two years ago. Sen. Jon Kyl (R), McCain's appointed successor, resigned in late 2018, and McSally was appointed to occupy the seat, taking office in January 2019.

The race is critical for Republicans, who are fighting to maintain their majority in the Senate. Republicans essentially hold a three-seat majority, and they cannot afforded to cede ground to Democrats.

The race has taken on even more importance in the wake of Ruth Bader Ginsburg's death. If Republicans cannot confirm Ginsburg's successor, Amy Coney Barrett, quickly enough, the party may have one less vote in Barrett's favor.

That's because McSally and Kelly are competing in a special election to fulfill the final two years of McCain's term. If Kelly wins, he could be seated as soon as Nov. 30 — not in January 2021 like all other election winners.

What are the details?

In an essay for the Arizona Republic, Tom Stafford, Charlie Duke, and Jack Lousma — who have spent about 2,400 hours in space combined — endorsed McSally and explained why Kelly is unfit for the job.

Of McSally, they wrote:

McSally delivered results for Arizona. Just look at the stats: She was ranked as one of the most bipartisan senators last year and tied for the most bills passed into law. Just this year, she introduced legislation to lower the cost of prescription drugs, started the national Veterans Treatment Courts to help improve the lives of veterans, and she helped write the legislation that gave families and small businesses help to get through the novel coronavirus. Whether it's helping secure funds for Fort Huachuca, leading on the Drought Contingency Plan or getting Congress to pass land exchanges that give local control back to Arizona, Martha springs into action when her constituents reach out to her with a problem.

On the other hand, the astronauts blasted Kelly, writing that "having 'astronaut' on your resume does not mean you'd be a good U.S. senator."

"Mark Kelly is hoping Arizonans are so impressed with his background that they ignore the fact that he's supported radical gun control activists, that his plan for the eventual government takeover of health care would end Medicare as we know it, and that he'd vote to raise our taxes," they wrote.

"On some of the more extreme policies of the Democrat Party, Mark has tried to stay quiet. We can only think of one reason: He doesn't want to answer for his liberal political views and policies and those of his party," the astronauts added.

The astronauts went on to write that Kelly must answer for the Democratic Party, which they noted has become more progressive in recent years.

"Mark Kelly has to answer for the policies of his party because if he were elected, that's what would become law in a Democrat-controlled government," they wrote. "McSally has delivered for Arizona, while Mark Kelly embraces Democrat ideology that would be bad for our country — leaving us with less freedoms, less security and less control of our lives."

What do the polls say?

Unfortunately for McSally, the polls have good news for Kelly.

According to the RealClearPolitics average, Kelly leads McSally by 6% in the run-up to the election, a gap significant enough to worry Republicans about losing the seat.