The historic partisan rancor surrounding Supreme Court nominee Brett Kavanaugh could wind up helping Republicans keep control of the Senate in November, new polls and on-the-ground data suggest, as the controversy appears to galvanize conservative voters.

Political headwinds normally work against the party of incumbent presidents in their first midterm elections. According to an analysis by former George W. Bush administration official Bruce Mehlman, in the past 11 such midterm seasons, new presidents saw their party make net gains only once in the House, four times in the Senate and zero times in state gubernatorial contests.

But a new round of Fox News battleground polls, released Wednesday, suggests the 2018 midterms might buck that trend -- at least in the Senate, where the 35 seats up for election largely are in GOP-leaning states.

The surveys show a noticable uptick in Republican enthusiasm across the board in the past several weeks, concurrent with the increasingly heated confrontation between both parties over Kavanaugh's confirmation and the sexual misconduct allegations leveled against him. The Senate is viewing the supplemental background investigation on those claims Thursday. While Democrats have complained about that process, sources say the review did not corroborate the allegations; a confirmation vote is expected as early as this weekend.

READ THE FULL RESULTS OF THE FOX NEWS SENATE POLLS

Amid that showdown, President Trump has drawn attention to polls suggesting the GOP base is fired up.

"The harsh and unfair treatment of Judge Brett Kavanaugh is having an incredible upward impact on voters," he tweeted Thursday.

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On the heels of the Fox News polls, he also tweeted: "Wow, such enthusiasm and energy for Judge Brett Kavanaugh. Look at the Energy, look at the Polls. Something very big is happening."

Democrats, likewise, are working to fire up their own party over the Kavanaugh clash, arguing that Republicans from Trump on down have disrespected accuser Christine Blasey Ford and others by questioning their accounts. Their concerns tap into the powerful #MeToo movement, which could still result in a backlash for GOP candidates in House races in swing districts.

"The fight over Judge Kavanaugh is increasing base intensity for both parties, helping Democrats with white college-educated women in suburban House districts while bolstering Republicans among evangelical voters in the many rural red state Senate contests," Mehlman told Fox News. He recently authorized an analysis outlining how some other major factors, including the economy and record-high levels of spending, are will impact the upcoming vote.

But Republicans are fighting on already-favorable turf in Senate races. And the Fox News polling shows an overall surge in GOP voter enthusiasm. Compared with early September, the number of Republicans feeling “extremely” interested in the upcoming election is up by 2 points in Arizona, up by 9 points in Indiana, up 8 points in both Missouri and North Dakota, and up 11 points in Tennessee. In each state, Republicans are now just as likely as Democrats to say they are extremely interested -- erasing an edge Democrats had in several states last month.

Voter interest is directly linked to turnout, which Republican leaders feared would be so low as to offset some of the inherent advantages they have this year in the Senate. Only nine GOP-controlled seats there are up for grabs in 2018, compared with a whopping 26 for Democrats -- and some of those Democrat-controlled seats are in states that went by wide margins for Trump in 2016, including North Dakota, Missouri and Indiana.

At a rally Tuesday in Montana, Vice President Mike Pence's vocal support of Kavanaugh got a bigger rise out of the crowd than anything he said about tax reform, ObamaCare or even 2016’s most reliable rallying cry – a promise to build a border wall.

“You know, Judge Brett Kavanaugh is a man of integrity with impeccable credentials,” Pence said, to uproarious cheers and applause, at the end of a riff about other conservative judges Trump has nominated.

“I think what it’s done is basically galvanize, certainly, the Republican voters,” said Montana Republican Senate candidate Matt Rosendale, who is hammering his opponent, Sen. Jon Tester, D-Mont., for his pledge to vote “no” on the nominee.

Voters also appeared particularly energized in Missouri, which Fox News polls show is tied up at 43 percent apiece for incumbent Democratic Sen. Claire McCaskill and Republican challenger Josh Hawley. Just three weeks ago, McCaskill was up 44-41 percent. Last week, even before California professor Christine Blasey Ford testified against Kavanaugh, McCaskill announced that she would not support the nominee.

ADVERTISING BACKFIRE: REPUBLICAN SENATOR ASKS MCCASKILL TO REMOVE HIM FROM TV SPOT TOUTING HER 'BIPARTISAN' CREDENTIALS

That decision seems to be costing McCaskill some key support. Crucially, according to Fox News polling, among the 28 percent of voters who say they could still switch candidates, almost twice as many say McCaskill voting against Kavanaugh’s confirmation would make them less inclined to back her.

"The priority in Democratic infrastructure is to win the House."
— Democratic strategist Jesse Ferguson

North Dakota shows an even clearer picture.

Vulnerable North Dakota Democratic Sen. Heidi Heitkamp, who remains undecided on Kavanaugh, appeared to be treading carefully after McCaskill's loss of support. Fox News' polling shows Republican challenger Kevin Cramer now leading by 12 points (53-41 percent). Last month, he was up by only 4 points (48-44 percent).

For their part, Democrats are also trying to leverage Kavanaugh to boost their base. In a fiery speech outside the Supreme Court Wednesday, House Minority Leader Nancy Pelosi, D-Calif., likened Trump's support for Kavanaugh to his outreach to North Korean dictator Kim Jong Un and Russian President Vladimir Putin.

Pelosi, who had vowed to "avenge Obama" by fighting Kavanaugh before his nomination was even announced, emphasized the importance of voters mobilizing to see results in Washington.

Analysts and polling suggest that Democrats, despite the upsurge in Republican enthusiasm, still have good odds to retake the House in November, where all of the seats are up for grabs.

“Our guys are taking a beating,” GOP consultant Rob Simms told The Washington Examiner on Tuesday, saying that House Republican candidates are being badly outspent by well-funded Democratic groups.

A new poll from Quinnipiac University showed that 49 percent of voters preferred that the Democrats take back Congress, compared with 42 percent for Republicans.

“For the first cycle in a decade, the priority in Democratic infrastructure is to win the House,” Democratic strategist Jesse Ferguson told the Examiner. “The Trump administration is fueling the desire of Democrats to win the House so that we have at least one arm of government.”

Fox News' Peter Doocy and Dana Blanton contributed to this report.