Data: Axios research and FiveThirtyEight's Trump Score. See our methodology here. Chart: Naema Ahmed, Sara Wise, Juliet Bartz, Orion Rummler/AxiosSen. David Perdue, whose upcoming runoff election in Georgia could help determine which party controls the Senate, has been President Trump’s top loyalist in the upper chamber, according to the "Axios on HBO" Trump Loyalty Index.Why it matters: In the wake of a presidential election largely seen as a referendum on Trump, Perdue’s unbreakable allegiance to the president effectively makes Trump an issue again in the runoff. Perdue received a 91 out of 100 on our Trump Loyalty Index — the highest score among the Senate’s 53 Republicans — by voting with the president 95% of the time and defending him through seven controversies that would have crushed most politicians.Perdue’s score is also the second highest among the 201 Republican members of Congress who have held office throughout Trump’s term, falling two points short of Rep. Glenn Grothman (R-Wisc.), who topped the list with a 93. Between the lines: Even though President-elect Joe Biden leads Trump in Georgia as the state heads to a recount, Perdue has doubled down on his loyalty to the president. Earlier this week, Perdue and fellow Georgia Sen. Kelly Loeffler (R), who's also in a runoff on Jan. 5, called on Republican Secretary of State Brad Raffensperger to resign over a failure to deliver "honest and transparent elections," although the senators did not provide evidence. The bottom line: Despite Georgia trending blue in a presidential race for the first time since 1992, Perdue and Loeffler’s fierce loyalty to the president signals that they see tapping into and turning out Trump’s base as their most promising path to retaining their seats.If they’re right, it would be yet another reflection that this election has not been the complete repudiation of Trump that Democrats hoped for.