The U.K., often a wingman to the United States in defense, is pushing its ally to stand firm against President Vladimir V. Putin, amid fears that Russia poses an existential threat to Europe.
When David Cameron, Britain’s foreign secretary and onetime prime minister, visited Washington last month, he took time out to press the case for backing Ukraine with Representative Marjorie Taylor Greene, the far-right Georgia Republican who stridently opposes further American military aid to the country.
Last week, Boris Johnson, another former prime minister, argued that the re-election of Donald J. Trump to the White House would not be such a bad thing, so long as Mr. Trump comes around on helping Ukraine. “I simply cannot believe that Trump will ditch the Ukrainians,” Mr. Johnson wrote in a Daily Mail column that read like a personal appeal to the candidate.
If the “special relationship” between Britain and the United States has taken on an air of special pleading in recent weeks, it is because Britain, rock solid in its support for Ukraine, now views its role as bucking up an ally for whom aid to the embattled country has become a political obstacle course.
British diplomats said Mr. Cameron and other senior officials had made it a priority to reach out to Republicans who were hostile to further aid. For reasons of history and geography, Britain recognized that support is not as “instinctive” for Americans as it for the British, according to a senior diplomat, who spoke on condition of anonymity because of the diplomatic sensitivity of the matter.
Unlike in the United States, where Ukraine has gotten tied up in a dispute with Republicans over President Biden’s border policy and come under the shadow of a dismissive Mr. Trump, support for Kyiv in Britain has stayed resolute, undiminished, and nonpartisan in the two years since Russia’s invasion.
Even in an election year, when the Conservative government and its Labour Party opponents are clashing over almost everything, there is not a glimmer of daylight between them on Ukraine, the biggest foreign policy challenge facing the country.
When Prime Minister Rishi Sunak recently announced 2.5 billion pounds ($3.2 billion) of additional aid for Ukraine, the Labour leader, Keir Starmer, instantly lent his support. Britain, the third-largest supplier of weapons after the United States and Germany, was the first major power to commit to new aid in 2024.
“We will remain united across our political parties in defense of Ukraine against that aggression from Putin,” Mr. Starmer said. On a visit to British troops deployed in Estonia, near the Russian border just before Christmas, he warned of the problems that fester “when politics goes soft on Putin.”
That political consensus mirrors public opinion in Britain. Some 68 percent of people favor military assistance to Ukraine, and 53 percent say that aid should flow there “for as long as it takes,” according to a British Foreign Policy Group survey in July.
Many Britons view the war in Ukraine — just over three hours away by plane — as almost on their doorstep, and their support reflects a fear that a Russian victory would pose an existential threat to the security of Europe and Britain. Addressing the Ukrainian Parliament earlier this month, Mr. Sunak described military aid as “an investment in our collective security” and said, “if Putin wins in Ukraine, he will not stop here.”
Britain’s army chief, Gen. Patrick Sanders, warned in a speech on Wednesday that Britons were now a “prewar generation,” who could be pressed into service to confront a military threat to Europe from an emboldened Russia. Downing Street later clarified that General Sanders was not opening the door to peacetime conscription.
There is ample precedent for Britain trying to steady a wavering United States in international conflicts. In 1990, when President George H.W. Bush was struggling to build a United Nations coalition to oppose Iraq after it invaded Kuwait, Margaret Thatcher famously told him, “Remember, George, this is no time to go wobbly.”
At other moments, Britain plays the role of America’s ready wingman. On Monday, it joined the United States in a second round of airstrikes against Houthi militants in Yemen, just hours after a phone call between Mr. Sunak and Mr. Biden, in which they agreed on the need to combat Houthi attempts to block commercial shipping in international sea lanes.
Malcolm Chalmers, the deputy director general of the Royal United Services Institute, a London think tank, said the British American cooperation on Yemen, and Britain’s prodding of Washington on Ukraine, captured the push-pull dynamic that has characterized the trans-Atlantic relationship for decades.
“People sometimes mischaracterize U.K. security policy as being a poodle of the U.S.,” he said. “The U.K. puts a very close value on its relations with the U.S., but that doesn’t mean we won’t push the U.S. if we feel it is not in the right place.”
The contrast between the allies on Ukraine has been especially stark, in part because both are entering election cycles in which such policies are easily held captive to broader political debates. Brexit-era populist figures like Nigel Farage still roam restlessly on the fringe. Mr. Farage, a conspicuous ally of Mr. Trump who shares his softer views of President Vladimir V. Putin, is backing a new anti-immigration party, Reform U.K., which some Tory lawmakers fear will siphon votes from them.
