WASHINGTON — Republicans got everything they wanted from Brett Kavanaugh's hotly contested confirmation — a fired-up GOP base and a conservative Supreme Court justice for life. But they worry now it was achieved too soon to affect the midterms.

Republicans celebrated the reaction to Kavanaugh's testimony before the Senate Judiciary Committee after limited polling suggested their voters had closed the enthusiasm gap with Democrats. But some strategists are concerned about how far the 'Kavanaugh effect' can carry the party post-confirmation and a month of unpredictable news cycles lies ahead until Election Day.

"I certainly think this exercise woke (Republicans) up and hit the right electoral pleasure centers, which we seem to be seeing reflected in some of the polling, but my fear would be peaking a hair too soon," Liam Donovan, a former staffer at the National Republican Senatorial Committee, told NBC News.

A widely cited NPR/Marist poll last week showed Republicans cutting the Democrats' generic ballot lead — would you vote for a Republican or Democrat? — in half to six points and their voters catching up in interest in the midterms.

Some GOP pollsters also reported similar changes in internal polls, but public data is still sparse and nonpartisan election raters have yet to declare a sweeping shift in the landscape toward Republicans, especially in the House, where Democrats still appear well-positioned to win a majority in November.

A worst-case scenario for the GOP would be if Democratic-leaning voting blocs are still nursing fierce grievances over Kavanaugh's confirmation, which came after Dr. Christine Blasey Ford accused him of sexual assault in her testimony before the Judiciary Committee, while Republicans move on to focus on other concerns.

Progressive groups have reported spikes in fundraising during the nomination fight. Already, liberal activists have raised over $2 million to back a challenger to Sen. Susan Collins, R-Me., who voted to confirm Kavanaugh, in 2020.

"Whichever side loses the confirmation battle is ultimately going to see their supporters rally to a larger degree," said Adrian Gray, a Republican pollster.

A parallel might be last year's GOP tax cuts, which prompted a burst of improved polling and optimistic pronouncements from Republicans. President Donald Trump's voters who were skeptical of the bill's tilt to the wealthy but rallied around its final passage. Over time, however, enthusiasm faded and Democrats now seem confident attacking the tax plan in races around the country, even in districts where tax cuts have historically been a powerful motivator for Republicans.

At the same time, Republicans might not need a large bump from Kavanaugh to have a decisive impact in November.

Control of the Senate hinges on a small number of closely contested races in red states that Trump won by large margins. Most Republicans would happily sacrifice a few House seats to a backlash among suburban women if it meant tipping critical Senate races to the GOP in North Dakota, Montana, Missouri, Tennessee and West Virginia and preserving the party's edge in the Senate.

Republicans crowed when two polls showed Senator Heidi Heitkamp, D-N.D,. trailing Rep. Kevin Cramer, R-N.D., by double digits. A Valley News Live poll found voters in the state supported the Kavanaugh nomination by a better than 2-1 margin. Democrats had conceded she was their shakiest incumbent, making it difficult to assess how much of her deficit was was due to the Kavanaugh fight. Heitkamp voted against his confirmation, citing concerns about his "current temperament, honesty and impartiality."

In the Montana Senate contest, the authoritative Cook Political Report shifted its rating to "toss-up" from "lean Democrat" partly in response to the decision of Sen. Jon Tester, D-Mont., to vote against Kavanaugh.

Chris Hayden, spokesman for the pro-Democratic Senate Majority PAC, said their own polling showed no obvious gains in red state races for Republicans since the Kavanaugh hearing.

"We looked at the data and so far Kavanaugh has not been a huge issue in these races," he said. "Republicans continue to try to change the subject from health care and this is the latest example of how that's just not happening."

In two key red-state contests, Democrats sided with Republicans on confirmation, giving them an opportunity to showcase their independence from their party at the risk of demoralizing some core supporters.

In West Virginia, Sen. Joe Manchin, D-W.Va., announced he was a "yes" on Kavanaugh minutes after Collins provided the decisive vote. And in Tennessee, former governor and Democratic Senate nominee Phil Bredesen said he would have supported Kavanaugh's confirmation. In response, Priorities USA, a leading Democratic super PAC, announced it would not support either candidate.

"It's a devastating development for the country, but I do think, politically, this is the worst outcome for Republicans," said Jesse Lehrich, communications director at Obama-backed Organizing For America.

"An open seat due to 'Dem obstruction' would have been a serious motivator for the right."