Polls show tight races in two key states featuring Senate races for Republican-controlled seats.

Approximately 50% of likely Wisconsin voters are supporting Sen. Ron Johnson, the race's Republican incumbent. However, right on Johnson's heels is Lt. Gov. Mandela Barnes with 49% of likely voters, according to a new batch of CNN polls conducted by SSRS.

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Ron Johnson

Sen. Ron Johnson, R-Wis. (Bill Clark/CQ-Roll Call, Inc via Getty Images)

Barnes is seeking to unseat Johnson in a race the Democratic Party is counting on to win the Senate majority. However, Barnes' supporters worry he is not getting the support he needs to win on Election Day.

Democratic strategist Irene Lin told Politico that though the Senate Majority PAC is not completely at fault, the super PAC's ads "clearly didn’t penetrate message-wise."

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Democratic U.S. Senate candidate Mandela Barnes answers a question during second debate

Democratic U.S. Senate candidate Mandela Barnes speaks during a televised debate Thursday, Oct. 13, 2022, in Milwaukee. (AP Photo/Morry Gash)

In Pennsylvania, Democratic Lt. Gov. John Fetterman is running against Republican opponent Dr. Mehmet Oz for the Senate seat of outgoing Sen. Pat Toomey. 

Fetterman holds approximately 51% of likely voters polled by SSRS — with Oz at 45%, a lead that is just outside the poll's margin of error of 4.1 percentage points.

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The pair are scheduled to appear in the only debate of the race Tuesday night.

John Fetterman with Biden

President Biden is greeted by Pennsylvania Lt. Gov. and Democratic senatorial candidate John Fetterman upon arrival at Pittsburgh International Airport in Pittsburgh, on Oct. 20, 2022. (MANDEL NGAN/AFP via Getty Images)

President Biden said during a visit to Pennsylvania Thursday that voters should back Democratic Senate candidate Fetterman over his Republican opposition, Dr. Oz, because the "rest of the world is looking."

Attempting to instill urgency in voters to turn out for what is expected to be a tight race — and one that could potentially decide the majority of the U.S. Senate — Biden said the implications of the race could vastly change U.S. policy. 

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Earlier this year, former President Trump endorsed Oz's candidacy during the state’s Republican primary. The endorsement has helped narrow Oz’s once 10-point deficit.

The polls were conducted by SSRS between Oct. 13 and Oct. 17 in Pennsylvania and Wisconsin. 

Dr. Oz speaking into a microphone

Republican U.S. Senate candidate Dr. Mehmet Oz hosts a safer streets community discussion at Galdos Catering and Entertainment on Oct. 13, 2022, in Philadelphia. (Mark Makela/Getty Images)

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SSRS used a sample size of 905 likely voters in Wisconsin, with a margin of error of 4.2. 

The Pennsylvania sample size was 901 likely voters.

Fox News' Lawrence Richard contributed to this report.