WASHINGTON — Over more than eight hours last Thursday night and into Friday morning, Rep. Kevin McCarthy hit on many issues as he spoke on the House floor in an unsuccessful effort to thwart House passage of President Joe Biden’s social safety net and climate change bill.

But among his most audacious assertions was that Biden was to blame for the country’s failure to quell the pandemic.

McCarthy, R-Calif., used this line of attack even as members of his own Republican Party have spent months flouting mask ordinances and blocking the president’s vaccine mandates, and the party’s base has undermined vaccination drives while rallying around those who refuse the vaccine. Intensive care units and morgues have been strained to capacity by the unvaccinated, a demographic dominated by those who voted last year for former President Donald Trump.

As of mid-September, 90% of adult Democrats had been vaccinated, compared with 58% of adult Republicans.

Yet McCarthy, the House Republican leader, pressed his point: “I took President Biden at his word; I took him at his word when he said he was going to get COVID under control,” he declared in the dead of night. “Unfortunately, more Americans have died this year than last year under COVID.”

As cases surge once again in some parts of the country, Republicans have hit on a new line of attack: The president has failed on a central campaign promise — to tame the pandemic that his predecessor systematically downplayed. Democrats are incredulous, dismissing the strategy as another strand of spaghetti thrown at the wall.

White House spokesperson Andrew Bates hit back hard: “If COVID-19 and inflation had lobbyists to help them kill more American jobs, Kevin McCarthy would be their favorite member of Congress,” he said. “He is actively undermining the fight against COVID, which is driving inflation.”

Chris Taylor, a spokesperson for the Democratic Congressional Campaign Committee, called House Republicans “COVID’S biggest promoter” for “recklessly hand-waving lifesaving vaccines” and for promoting ivermectin, an anti-parasitic drug falsely said to cure COVID-19.

As of Wednesday, nearly 775,000 Americans have died from the virus and over 48 million have been infected, according to Johns Hopkins University.

But Republican strategists and pollsters say Democrats should not be so quick to brush off the criticism, even if many COVID-19-related deaths this year were among those who ignored Biden’s entreaties to get vaccinated.

“McCarthy’s first hit on Biden is a competence hit — that he sold himself to voters as the guy who can make a difference in the fight against COVID, yet more Americans are dying,” said Neil Newhouse, a Republican pollster who has surveyed voters on the issue. “The bottom line is that Republicans have always been more focused on the economic impact of the pandemic, and now we’re seeing independents and swing voters expressing concern about those impacts as well: supply chain, inflation, jobs, stores not being open or having what they need.”

He added, “There is a sense that Biden’s presidency is falling short on its promises.”

The Thanksgiving wave is the latest surprise in a pandemic that is nearing its two-year mark. The nation’s 14-day average of new infections is up 25% to more than 94,000 new cases a day, with the upper Midwest again the hottest of hot spots.

At the same time, the efficacy of the coronavirus vaccines is holding, according to the latest data from the Centers for Disease Control and Prevention. Unvaccinated people are 5.8 times as likely to test positive than fully vaccinated people and 14 times as likely to die if infected.

The partisan gap in infection and vaccination rates is only slightly narrowing.

The most Republican counties have 2.78 times as many new cases than the most Democratic counties, down from three times as many a month ago, according to Democratic health care analyst Charles Gaba, using data from Johns Hopkins.

The death rate in those Republican counties is nearly six times as high as the death rate in the Democratic counties.

It is unclear whether the pandemic or the vaccine mandates devised to beat it are causing the president’s approval ratings to slide.

Newhouse’s firm, Public Opinion Strategies, found Biden’s overall approval rating for his handling of the pandemic to be a relatively fine 51% in October, down from 69% in April but only from 53% in August.

But in the suburbs, where the 2020 presidential race was won, the president’s approval rating on the pandemic has slipped since August from 51% to 45%. And among white men, the slide is more pronounced, from 58% in April to 43% in August and 32% in October.

Republican lawmakers are continuing to try to block vaccine mandates at the local, state and federal levels.

But White House officials say the president has made substantive progress toward ending the pandemic.

At this time last year, 250 million adults were not vaccinated. Now about 47 million remain without inoculation.