Republican pollster and strategist Frank Luntz told CNBC on Monday that President Donald Trump’s persistent attacks on election integrity could hurt the GOP in the upcoming Georgia Senate runoffs, which will determine the balance of power in the upper chamber.”If he continues to disillusion voters … by saying that the elections were rigged and that your vote doesn’t matter, this could have severe consequences for the administration in trying to keep those two seats Republican,” Luntz said on “Squawk Box.”The GOP holds a two-seat advantage in the Senate, 50-48, according to NBC News projections. The remaining two vacancies in Georgia will be decided in run-offs Jan. 5. One race is between Republican Sen. Kelly Loeffler and Democrat Raphael Warnock, while the other pits incumbent GOP Sen. David Perdue and Democratic challenger Jon Ossoff.A pair of Democratic victories would give the party control of the Senate — along with the House and presidency. That would likely alter significantly the trajectory of policymaking in Washington under Democratic President-elect Joe Biden, who won Georgia’s presidential race. Luntz has previously described the Jan. 5 runoffs as “the most important Senate elections in modern times.”Trump has not, however, conceded the Nov. 3 presidential election to Biden despite various media organizations, including NBC News, calling the race more than two weeks ago. Trump and his campaign have instead been waging — mostly unsuccessful — legal fights in various battleground states.The president repeatedly launched baseless attacks on the integrity of election, falsely claiming he won and suggesting without evidence that widespread voter was the reason for Biden’s advantage. Trump’s personal lawyer, Rudy Giuliani, also has promoted far-fetched conspiracy theories as part of an attempt to overturn the election result.A coalition of U.S. government security agencies also has defended the integrity of the election, calling it “the most secure in American history.” The statement added, “There is no evidence that any voting system deleted or lost votes, changed votes, or was in any way compromised.”There also has been a growing number of elected Republicans also have called on Trump to concede, including Pennsylvania Sen. Patrick Toomey.”I have fully supported the president pursuing every plausible strategy — recounts and litigating irregularities — but at some point you exhaust those possibilities,” Toomey said Monday, also on “Squawk Box.” “I think the president has reached that point in Pennsylvania. He appears to have reached that point in Georgia. Michigan wasn’t even close.” He added, “I can assure you I am not alone in this view among Republican senators.”Luntz said his recent polling indicates Republican voters in Georgia appear more interested in the January runoffs, with 80% of GOP voters saying they’re definitely planning to vote compared with 70% of Democrats. However, he said if Trump continues to falsely insulate that the election was rigged against him, his own voters may be dissuaded his from turning out in January. It’s a concern held by other Republicans, according to reporting from Axios’ co-founder Mike Allen.”I would argue that Donald Trump says, and does, over the next six weeks is going to determine the outcome of the Georgia Senate race and well may determine the outcome of our country overall,” said Luntz. “We still find that 55% of Trump voters in Georgia … believe Donald Trump was elected president and so they’re mad,” Luntz added.Biden’s victory in Georgia was certified Friday.