The battle for control of the Senate is looking worse and worse for Democrats, who just a month ago saw a path to the majority but now increasingly look like they could lose more seats and have a smaller minority next year.

Republicans have seen a bump in the polls in several key races since Labor Day. They believe momentum has flipped to their party since the fight over Supreme Court Justice Brett Kavanaugh Brett Michael KavanaughTrump faces tricky choice on Supreme Court pick The Hill's 12:30 Report: Trump stokes fears over November election outcome The Hill's Morning Report - Sponsored by Facebook - Trump previews SCOTUS nominee as 'totally brilliant' MORE polarized the electorate, hurting Democrats running for reelection in states where President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE is popular.

Two states where Democrats had hopes of pulling major upsets — Texas and Tennessee — have moved in favor of Republicans. Races in Nevada and Arizona, two other states where Democrats had hoped to make gains, remain tight, but Republicans feel more confident about their candidates.

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Meanwhile, the tide has moved against Democratic candidates in a couple of states that Trump won by double digits in 2016.

In North Dakota, Democratic 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 has fallen behind by double digits. And in Montana, Sen. Jon Tester Jonathan (Jon) TesterDemocrats shoot down talk of expanding Supreme Court Pence seeks to boost Daines in critical Montana Senate race This World Suicide Prevention Day, let's recommit to protecting the lives of our veterans MORE (D), who seemed poised for victory a month ago, has seen his race tighten amid attacks by the president.

There is some good news for Democrats in the polls.

Sen. Joe Manchin Joseph (Joe) ManchinSenate passes resolution reaffirming commitment to peaceful transition of power Hopes for DC, Puerto Rico statehood rise Manchin defends Supreme Court candidate Barrett: 'It's awful to bring in religion' MORE (D-W.Va.), the only Democrat to back Kavanaugh’s confirmation, has maintained a healthy average lead of 9 points in the polls, despite running in a state that Trump won by a whopping 42 points in 2016.

And Sen. Joe Donnelly Joseph (Joe) Simon DonnellyHarris faces pivotal moment with Supreme Court battle Trump meets with potential Supreme Court pick Amy Coney Barrett at White House Names to watch as Trump picks Ginsburg replacement on Supreme Court MORE (D-Ind.), long seen as vulnerable, is hanging onto an average poll lead of 3 points, despite voting against Kavanaugh.

But there are other chances for Republicans to grow their 51-49 majority.

Democratic 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’s (Mo.) reelection race against Republican Josh Hawley remains tight, while 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-Fla.) has drawn a tough challenger in Gov. Rick Scott (R).

In New Jersey, 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) is ahead in polls but Republicans still think they have a chance of pulling off an upset.

Democrats argue that they have an advantage on health care, the No. 1 issue for voters.

They are trying to capitalize on recent comments by Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellTrump 'no longer angry' at Romney because of Supreme Court stance On The Money: Anxious Democrats push for vote on COVID-19 aid | Pelosi, Mnuchin ready to restart talks | Weekly jobless claims increase | Senate treads close to shutdown deadline The Hill's Campaign Report: Trump faces backlash after not committing to peaceful transition of power MORE (R-Ky.), who blamed Social Security and Medicare for the nation’s deficit problems and said Republicans may take another shot at repealing ObamaCare next year.

“In the last week Fox News, CBS and Washington Post-ABC polls all confirmed that the top issue this election is health care. Then Mitch McConnell reminded voters he wants to take away coverage for pre-existing conditions and target Medicare and Social Security,” said Democratic Senatorial Campaign Committee spokesman David Bergstein.

“This isn't what Republicans want to be talking about, and we appreciate his help reminding voters exactly what's on the ballot,” he added.

Despite the Democrats’ focus on health care, however, their top GOP target, Nevada 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, has remained steady in polls despite his vote to repeal ObamaCare. FiveThirtyEight gives him a nearly 56 percent chance of winning reelection.

Sen. Ted Cruz Rafael (Ted) Edward CruzThe Hill's Morning Report - Sponsored by Facebook - Trump previews SCOTUS nominee as 'totally brilliant' Cruz blocks amended resolution honoring Ginsburg over language about her dying wish Trump argues full Supreme Court needed to settle potential election disputes MORE (R), who has increased his lead over Rep. Beto O’Rourke (D-Texas), says the Kavanaugh debate helped him and other GOP candidates.

“Absolutely,” Cruz said. “I think the Democrats' behavior in the Kavanaugh hearing was appalling and I think a great many Texans were deeply disturbed at the partisan games and the political circus where they were willing to smear Judge Kavanaugh and his family to score political points.”

The race between Cruz and O’Rourke was tightest in early September when Cruz’s lead in the Real Clear Politics poll average was only three points. But as the battle over Kavanaugh heated up, he saw his lead grow to 5 and now 7 points, according to an average of polls compiled by RealClearPolitics.com.

In Tennessee, the RealClearPolitics polling trend lines of Democratic candidate Phil Bredesen and Republican Rep. Marsha Blackburn Marsha BlackburnHillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Key Democrat opposes GOP Section 230 subpoena for Facebook, Twitter, Google Senate panel threatens subpoena for Google, Facebook and Twitter executives MORE (Tenn.) crossed in late September, when the vicious Supreme Court fight was peaking in national attention.

Blackburn now has a 6.5-point lead in the RealClearPolitics polling average, a substantial improvement over most of the late spring and summer, when she trailed by an average of 5 points.

“You can probably thank Brett Kavanaugh for that. Everybody that I talked to that was on the bubble or maybe even for Bredesen — and I’m talking about Republicans — I haven’t talked to one of them since Kavanaugh that’s not saying I’m voting for Marsha,” said Chip Saltsman, a Tennessee-based GOP strategist.

Bredesen tried to blunt the impact of the Kavanaugh debate earlier this month by announcing his support for the nominee, which caused some of his volunteers to quit.

Democrats haven’t written off the contest at all.

A Washington-based Senate Democratic strategist argued that recent polls show Bredesen in a dead-heat with Blackburn. A Vanderbilt University survey released Thursday showed him ahead 44 percent to 43 percent. And a poll published Wednesday by Reuters showed Blackburn ahead by only 3 points, within the survey’s margin of error. But a New York Times/Siena College poll conducted around the same time gave Blackburn a 14-point lead.

The McCaskill-Hawley race is tight, but Republicans also think the Kavanaugh fight helped them in that state.

The RealClearPolitics polling trend lines have crossed, as McCaskill held a lead until mid-August but now trails slightly in an average of recent polls. A CNN poll from last month did show her ahead by 3 points and a Fox News survey showed her even with Hawley.

In Montana, a Gravis poll from June showed Tester with an 8-point lead while a follow-up Gravis survey in late September showed it had shrunk to 4 points.

Montana is also a top target of President Trump, who made his third trip to the state Thursday to hold a rally for Tester’s opponent, Matt Rosendale.

Rosendale has tried to take advantage of voters’ anger over Kavanaugh by drawing comparisons to how he was treated by Democrats on the Senate Judiciary Committee and how Tester treated Trump’s pick to head the Department of Veterans Affairs, Ronny Jackson, who withdrew after Tester led the opposition to him.

In North Dakota, Heitkamp has seen her poll numbers drop since Labor Day.

A Fox News poll from early September showed her trailing Republican Rep. Kevin Cramer Kevin John CramerAbortion stirs GOP tensions in Supreme Court fight Momentum growing among Republicans for Supreme Court vote before Election Day On Paycheck Protection Program, streamlined forgiveness is key MORE (N.D.) by 4 points but an NBC poll conducted later in the month showed Cramer ahead by 10 points and a follow-up Fox News poll released Oct. 3 gave Cramer a 12-point lead.

Senate Republican Conference Chairman John Thune John Randolph ThuneSenate passes resolution reaffirming commitment to peaceful transition of power Susan Collins faces political land mine with Supreme Court fight Abortion stirs GOP tensions in Supreme Court fight MORE (R), who comes from neighboring South Dakota, says he’s feeling good about knocking off Heitkamp, even while he acknowledges she’s a good retail campaigner.

“She’s a good retail campaigner,” he said, but added the race is Cramer’s to lose because “it’s kind of gotten nationalized.”

A Washington-based Senate Republican strategist said that Kavanaugh has polarized the electorate and as a result moderate GOP and independent voters are less likely to cross over and cast ballots for incumbent Democrats.

“It improved Republican prospects across the board,” said the strategist. “It polarized the electorate in red states and that’s the worst thing for Democrats who rely on a handful of Republican voters crossing the aisle and supporting them in order to get over the top."

In Arizona, Democratic Rep. Kyrsten Sinema has tried to distance herself from how her fellow Democrats treated Kavanaugh in the Senate.

“I was incredibly disappointed in the way that the Senate behaved during this confirmation hearing. It was a circus,” she said during a debate on Monday. “I was disappointed in the method that the Senate handled this. It felt like it really denigrated the work that the Senate should do.”