Pennsylvania Democratic Senate candidate Lt. Gov. John Fetterman and Republican candidate Dr. Mehmet Oz participate in the Nexstar Pennsylvania Senate at WHTM abc27 in Harrisburg, Pa., on October 25, 2022.
CNN  — 

Tell me who wins the Pennsylvania Senate race, and I’ll probably be able to tell you who controls the Senate next year.

Such a declarative statement may seem like hyperbole, but the stakes after Tuesday’s debate in Pennsylvania – which represents Democrats’ best chance of picking up a Republican seat – are sky high. And while we don’t know how voters will ultimately view what they saw (or heard in the aftermath) of the televised event, neither candidate has much room for error.

Republican Mehmet Oz had been closing in on Democrat John Fetterman, according to an average of polls. Fetterman sported a seven point advantage on September 1. By debate eve, the lead was down to two points.

The movement in the Pennsylvania polls is part of a trend we’ve seen in the swing states of 2022. Democrats have also lost ground over the last 60 days in Arizona, Nevada, New Hampshire – which they’re defending – and Wisconsin, which, after Pennsylvania, is their next-best pickup opportunity. In Georgia, which Democrats are also defending, they’ve been steady.

Democrats likely must win four of these six races – and right now, they hold an advantage in four. This includes Pennsylvania.

One interesting way to see the importance of Pennsylvania in the Senate math is by looking at statistical modeling from a website like FiveThirtyEight. If you know that Fetterman wins, then Democrats have a three-in-four chance of holding onto the Senate. If you know that Oz wins, then Republicans have a three-in-four chance of wresting away control of the Senate. No other state has that type of swing associated with it.

The big question is whether either candidate will be able to catapult from Tuesday’s debate to quell doubts voters had about them.

Much has been made of Fetterman’s health following a stroke earlier this year. A CBS News/YouGov poll before the debate found that 45% of voters believed that Fetterman was not healthy enough to serve in the Senate. That was up from 41% in September.

But Oz has his vulnerabilities too. Perhaps less spoken about in the press in the lead up to the debate was whether Oz could make himself more likable than he had been in the wake of a nasty May primary. Fetterman had a positive net favorability (favorable - unfavorable) rating in the last CNN/SSRS poll. Oz, however, had a -17 point net favorability rating.

Oz’s problem, of course, has been part of a larger problem facing Republican Senate nominees nationwide. Republicans in most of the competitive swing states have net n