Trump split the GOP and may have cost it the Senate as he pursued revenge against election officials in Georgia

• President Donald Trump's relentless attacks on Republican election officials and his attempts to undermine party leadership were most likely key elements in the party losing the Georgia runoffs and control of the Senate.
• Republicans had for months been warning that Trump's attacks on voting systems in the state could hurt their prospects in Tuesday's runoffs.
• In pursuing election-related conspiracy theories, Trump spent more time attacking state GOP officials than building a case for why the party's runoff candidates deserved victory.
• Both losing candidates in the runoffs, Sens. Kelly Loeffler and David Perdue, were steadfastly loyal to Trump, and their defeats call into question the value of Trump's support.

In the wake of their defeat in the Georgia runoff elections, when control of the US Senate slipped from their grasp, Republicans will be asking who was to blame.

Insider and Decision Desk HQ called the election early Wednesday morning, projecting victory for Jon Ossoff and the Rev. Raphael Warnock over the Republican incumbents David Perdue and Kelly Loeffler.

And a key factor in the GOP defeat is most likely President Donald Trump.

Georgia until 2020 was reliably Republican. And, historically the opposition performs strongly in elections after a new president is chosen, as voters seek to balance out the power of the incoming administration.

But both these trends were overturned.

For weeks Republican strategists in Georgia, in comments to publications including The New York Times, warned that Trump risked seriously damaging the party's performance.

They cited the president's doomed attempts to reverse the result of the presidential election and his relentless attacks on state GOP officials who have refused to erase President-elect Joe Biden's win in Georgia.

Trump's conspiracy theories about the integrity of voting systems in Georgia, they warned, would undermine trust in the contest among GOP voters.

As recently as last week, the GOP strategist and pollster Frank Luntz in a Fox News interview warned that the party's candidates in the state "may well lose on the fifth of January because of what the president is doing right now."

Sources told Jonathan Swan of Axios that Trump was so fixated with his election-fraud grievances that he was reluctant to campaign in Georgia.

Top Republicans, according to the outlet, think Trump is to blame for the loss after alienating suburban moderates and eroding trust in state election machinery.

As it became clear on Tuesday night that the Republicans were headed for defeat, one of the Republican officials who had been attacked by Trump returned the favor.

In the event of a Republican defeat, blame "falls squarely on the shoulders of President Trump," Gabriel Sterling, the voting-systems implementation manager for the Georgia secretary of state's office, told CNN.

His boss, Georgia's secretary of state, Brad Raffensperger, had been a repeated target of Trump in a clear sign of Republican infighting.

But it wasn't just his attacks on voting systems in Georgia and the officials charged with ensuring their integrity that played a role in the loss of the Senate.

As congressional Republicans began to acknowledge the reality that Biden would be sworn in as president on January 20, breaking from Trump's claim that it was he who was the true winner, the president began to wage a revenge campaign against them.

The president dramatically broke with GOP leadership to oppose the $600 stimulus checks in December's coronavirus relief package that they had negotiated with Democrats, calling for $2,000 instead. This undeniably hurt the GOP campaign in Georgia.

Only days before, Senate Majority Leader Mitch McConnell had acknowledged Biden's status as president-elect for the first time.

Thus the GOP went into the runoffs Tuesday a divided party, their Senate leadership undermined by Trump, and GOP officials in the state subjected not just to attacks from the president but threats from his hardcore supporters.

Loeffler and Perdue, the GOP candidates in Georgia, were forced to choose between backing the party's congressional leadership or the conspiracy theories of the president.

In the end, both candidates chose to back Trump, supporting his baseless election-fraud conspiracy theories, courting his far-right base, and winning the president's endorsement.

In the end, it was too little. This may also prompt the question of whether Trump's endorsement holds the value it once did, or whether his determination to attack the US electoral system, along with his own party, has made it a poisoned chalice.

The defeat is likely to deepen the divide between Republicans loyal to Trump's populist revolution and those keen to put the Trump years behind them and win back moderate voters who abandoned them for Biden.