Polls show a narrow plurality of Americans oppose the confirmation of Judge Brett Kavanaugh to the Supreme Court. Democrats hope that opposition helps them win back majorities in one or both chambers of Congress in the Nov. 6 midterm elections.

But intensity is what matters in politics. Voters in the key states that will determine party control of the House and Senate appear to have turned against the tactics Democrats have used to fan the allegations of sexual assault and other sexual misconduct against Kavanaugh.

“The Kavanaugh debate has dropped a political grenade into the middle of an electorate that had been largely locked in Democrats' favor for the past six months," Josh Holmes, a former top aide to Senate Majority Leader Mitch McConnell, R-Ky., told the website Axios.

Nationwide, an NPR/PBS NewsHour/Marist Poll released Wednesday found that the "wide Democratic enthusiasm advantage that has defined the 2018 campaign up to this point has disappeared.”

The poll noted: “In July, there was a 10-point gap between the number of Democrats and Republicans saying the November elections were 'very important.' Now, that is down to 2 points, a statistical tie."

Brand new Fox News polls show Republicans improving their position in Senate races in states carried by Donald Trump in 2016 where Democratic incumbents are now seeking re-election.

In North Dakota, GOP Rep. Kevin Cramer has opened up a 53 percent to 41 percent lead over Democratic Sen. Heidi Heitkamp – up from just four points in the same Fox News poll last month.

In Missouri, the Fox News poll shows Democratic Sen. Claire McCaskill tied with GOP state Attorney General Josh Hawley. In June, McCaskill had a four-point lead. Another new poll by the GOP group Missouri Rising Action gives Hawley an eight-point lead.

In Tennessee, where Republicans are defending an open seat, the latest Fox News poll shows GOP Rep. Marsha Blackburn opening up a lead over former Democratic Gov. Phil Bredesen.

Nate Silver, who analyzes polls for FiveThirtyEight.com, acknowledges that Republicans appear to be benefitting from the Kavanaugh fight. He writes: “In our Classic Senate forecast, for example, Republicans are now 77 percent favorites to hold the chamber, up from 68 percent before last week’s hearings.”

The impact of Kavanaugh on marginal House races, many of which are in districts with large numbers of suburban women, is less clear. But even there Silver notes that Republican chances of holding the House have risen from about 1 in 6 in mid-September to 1 in 4 today.

The reason for the greater enthusiasm of GOP voters to turn out can be explained by widespread anger at the unfair and outrageous tactics of the left in trying to block Kavanaugh’s Supreme Court confirmation. By shooting so low against Kavanaugh, Democrats may have actually shot themselves in the foot.

As the Wall Street Journal editorialized Thursday: “Republicans have figured out that if the left can willfully, even gleefully, destroy a man as distinguished as Brett Kavanaugh, they can and will do it to any conservative who threatens their grip on power. ..Voters know this is about the left’s will to power by any means necessary.”

Of course, it would be ironic if the all-out assault against Brett Kavanaugh wound up helping Republicans solidify their control of the Senate, which in turn would make it easier for President Trump to fill yet another vacancy on the Supreme Court.

But politics is full of ironies. Democrats may discover they should have thought more carefully before they launched their scorched-earth offensive to keep Kavanaugh off the Supreme Court.