Republicans are increasingly optimistic about their chances of expanding their narrow Senate majority after the polarizing confirmation battle over Supreme Court Justice Brett Kavanaugh Brett Michael KavanaughHarris faces pivotal moment with Supreme Court battle Poll: 59 percent think president elected in November should name next Supreme Court justice Feinstein 'surprised and taken aback' by suggestion she's not up for Supreme Court fight MORE.

In the weeks since a series of sexual misconduct allegations were raised against Kavanaugh, the GOP has seen candidates in the Republican strongholds of Texas and Tennessee strengthen their positions, putting possible upset bids by Democrats on hold.

Republicans are increasingly bullish on their chances of gaining a seat in North Dakota, where Sen. Heidi Heitkamp Mary (Heidi) Kathryn HeitkampHarris faces pivotal moment with Supreme Court battle Centrists, progressives rally around Harris pick for VP 70 former senators propose bipartisan caucus for incumbents MORE (D) has seen Republican Rep. Kevin Cramer Kevin John CramerMomentum growing among Republicans for Supreme Court vote before Election Day On Paycheck Protection Program, streamlined forgiveness is key McConnell shores up GOP support for coronavirus package MORE pull ahead in polls. They also believe they can defeat Sen. Claire McCaskill Claire Conner McCaskillMomentum growing among Republicans for Supreme Court vote before Election Day Democratic-linked group runs ads in Kansas GOP Senate primary Trump mocked for low attendance at rally MORE (D) in Missouri. Both Democrats voted against Kavanaugh's confirmation.

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“If you look at the polling we’ve seen in the last four or five days, it’s become clear that states like North Dakota and Missouri are moving in the Republicans’ direction,” said Matt Mackowiak, a GOP strategist.

“Most importantly, the opportunity that existed for Democrats in Tennessee and Texas looks like it's on the way out,” he said.

In Arizona and Nevada, widely seen as the best pickup opportunities for Democrats, recent polls suggest that the GOP is holding its own.

One poll released Wednesday by Phoenix-based pollster OH Predictive Insights showed Rep. Kyrsten Sinema (D-Ariz.) trailing Rep. Martha McSally Martha Elizabeth McSallyThe Hill's Campaign Report: Presidential polls tighten weeks out from Election Day Mark Kelly: Arizona Senate race winner should be sworn in 'promptly' New ABC/WaPost poll finds Trump edging Biden in Arizona, Florida MORE (R-Ariz.) by 6 points.

While most other recent polls show Sinema with a narrow lead, the race to succeed retiring Sen. Jeff Flake Jeffrey (Jeff) Lane FlakeHow fast population growth made Arizona a swing state Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Republican former Michigan governor says he's voting for Biden MORE (R-Ariz.) appears to be tightening. A Fox News poll conducted around the same time as the OH Predictive Insights survey showed Sinema ahead by 2 points – well within the poll’s 3.5-point margin of error.

In Nevada, an NBC News/Marist poll released earlier this month put Sen. Dean Heller Dean Arthur HellerOn The Trail: Democrats plan to hammer Trump on Social Security, Medicare Lobbying World Democrats spend big to put Senate in play MORE (R-Nev.) ahead of his Democratic challenger, Rep. Jacky Rosen Jacklyn (Jacky) Sheryl RosenHillicon Valley: Election officials prepare for new Russian interference battle | 'Markeyverse' of online fans helps take down a Kennedy | GOP senators unveil bill to update tech liability protections Google, Apple, eBay to meet virtually with lawmakers for tech group's annual fly-in Senate Democrats demand answers on migrant child trafficking during pandemic MORE (Nev.), by 2 points. Heller has long been seen as the most vulnerable GOP Senate incumbent.

“I think Senate races are tightening and that’s not a real surprise,” said Doug Thornell, a former deputy political director for the Democratic Senatorial Campaign Committee (DSCC). “As you get closer to an election, that typically happens. There’s more information that voters take in and on both sides see enthusiasm grow.”

The GOP’s best chances for picking up seats look to be in North Dakota and Missouri, but the party also sees opportunities in Montana and Indiana, two states Trump won easily in 2016, as well as Florida, another state won by Trump where Republicans have a strong candidate in Gov. Rick Scott.

West Virginia is another pick-up chance, though Sen. Joe Manchin Joseph (Joe) ManchinManchin defends Supreme Court candidate Barrett: 'It's awful to bring in religion' The Hill's Morning Report - Sponsored by Facebook - Trump, GOP allies prepare for SCOTUS nomination this week Trump meets with potential Supreme Court pick Amy Coney Barrett at White House MORE, the only Democrat to vote to confirm Kavanaugh, is holding on strong in polls. The Cook Political Report moved that race into the “Lean Democratic” column last month.

Republicans also see a longshot chance of flipping New Jersey, a deep-blue state that Hillary Clinton Hillary Diane Rodham ClintonDemocratic groups using Bloomberg money to launch M in Spanish language ads in Florida The Hill's Campaign Report: Presidential polls tighten weeks out from Election Day More than 50 Latino faith leaders endorse Biden MORE carried by 14 points in 2016.

A Stockton University poll released earlier this month showed a statistical dead heat in the race between Sen. Bob Menendez Robert (Bob) MenendezKasie Hunt to host lead-in show for MSNBC's 'Morning Joe' Senators ask for removal of tariffs on EU food, wine, spirits: report VOA visa decision could hobble Venezuela coverage MORE (D) and his Republican challenger Bob Hugin, with the incumbent Democrat carrying only a 2-point lead. Menendez was reprimanded by a Senate ethics panel in April after federal prosecutors dropped corruption charges against him.

Republican officials and operatives argued that the bitter fight over Kavanaugh’s confirmation has boosted their chances. They are hoping that the fight will energize their base in November in a year when Democrats have largely held an edge in voter enthusiasm.

At the same time, they say they are not taking anything for granted, and acknowledge the political winds can change quickly.

In North Dakota, they say it’s still possible Heitkamp could make a late comeback.

“Heidi’s never going to be done for,” one North Dakota Republican operative said. “Part of that is this state is cheap. A little bit of money can have a lot of impact. She’s a fighter, and she’s got nothing left to lose.”

In Missouri, a recent poll from Fox news showed Attorney General Josh Hawley (R) tied at 46 percent with McCaskill. A CNN poll conducted days earlier gave McCaskill a 3-point lead.

In Texas, Sen. Ted Cruz Rafael (Ted) Edward CruzCruz blocks amended resolution honoring Ginsburg over language about her dying wish Trump argues full Supreme Court needed to settle potential election disputes Press: Notorious RBG vs Notorious GOP MORE’s (R) polling numbers are on the rise. Two recent surveys by Emerson College and CBS News/YouGov showed the conservative firebrand pulling ahead by 5 and 6 points, respectively, over Rep. Beto O’Rourke (D-Texas).

In Tennessee, Rep. Marsha Blackburn Marsha BlackburnTaylor Swift on National Voter Registration Day: 'We need everyone' Democrats smell blood with new DHS whistleblower complaint Hillicon Valley: Election officials prepare for new Russian interference battle | 'Markeyverse' of online fans helps take down a Kennedy | GOP senators unveil bill to update tech liability protections MORE (R) held a 5-point lead in a Fox News poll earlier this month over former Tennessee Gov. Phil Bredesen. Another poll by CBS News/YouGov showed her ahead by 8 points.

In Florida, Sen. Bill Nelson Clarence (Bill) William NelsonDemocrats sound alarm on possible election chaos Trump, facing trouble in Florida, goes all in NASA names DC headquarters after agency's first Black female engineer Mary W. Jackson MORE (D) has seen his numbers rebound in recent polls against Scott. Hurricane Michael, which hit the state on Wednesday, has introduced a new uncertainty to that race.

Democrats have expressed optimism that the partisan fight over Kavanaugh will pump up their base.

“I think the pathway to the majority was always going to be difficult for Democrats,” Thornell said. “This is one of the most treacherous Senate maps either party has had in years. But it’s still in play because our incumbents are running strong campaigns, and we have put the GOP on defense in four states.”