It's not just the presidential election that matters big time.

What it means: The outcome in tonight's Georgia runoff elections will decide the fate of Biden's presidency, from whether he gets his Cabinet nominees to whether progressives get their tax hikes and public spending.

With control over the Senate majority and Washington political agenda at stake, the candidates searched for their winning message.

• Jon Ossoff declared $2,000 stimulus checks were on the ballot.
• Fellow Democrat Raphael Warnock — a pastor — said he was running to ensure economic fairness for Blacks and other minority and working-class voters.

The Republicans didn't promise confetti and unicorns; they warned — literally — of danger on the horizon.

• Kelly Loeffler ran TV ads branding Warnock "dangerous" and "radical."
• In an op-ed, David Perdue called Warnock "a radical extremist" and Ossoff "his far-left sidekick."

The cold calculus: If Democrats win both races, they gain a 50-50 split, and future Vice President Kamala Harris casts any tie-breaking votes.

• That added vote means the Democrats officially have the majority, and Sen. Chuck Schumer is the chamber's de facto majority leader.
• Sen. Mitch McConnell would stay on as minority leader.
• The two are likely to work out a power-sharing agreement, with an equal number of members from each party on Senate committees.

Key players to watch: Centrist Sens. Joe Manchin and Kyrsten Sinema, who are seen as the bulwarks within the Democratic Party against far-left legislation.

• Members of the "mod squad" — including Republican Sen. Mitt Romney — who shepherded the bipartisan coronavirus relief agreement in the final months of 2020 are also seen as central to any cross-party deal.
• Some progressive members on the Hill tell Axios' Alexi McCammond they’re waiting to push Biden on his eventual COVID-relief package, including proposals like recurring payments to Americans, until they know if they can get the measure through the Senate.

But, but, but: If Republicans win just one race — and Perdue is the bettors' choice — Democrats' dreams go up in smoke. Republicans hold court with at least a 51-49 vote margin.

• Cabinet nominees like Merrick Garland — who has been held back as a potential attorney general — are unlikely to move forward.
• Plans to force tax hikes and spending increases fizzle because Democrats can't use a 50-vote bloc to force them through the budget reconciliation process.

Be smart: The likely area of common ground no matter the outcome is infrastructure spending, as Axios reported last month. But even there, the amount of money that puts shovels in the ground will depend on who wins in Georgia.

Podcast alert: Listen as Sen. Amy Klobuchar tells Axios' Dan Primack and his Re:Cap podcast she expects more Republicans to come out in favor of certifying.