Democrats on the Senate Foreign Relations Committee have been careful to stay out of Thursday's U.K. elections, but some are nonetheless concerned about liberal counterpart Jeremy Corbyn's Labour Party and growing support in Britain for elements that embrace anti-Semitism.

While Corbyn is expected to finish behind incumbent Boris Johnson and his Conservative Party in the parliamentary elections, the Labour leader's popularity and an agenda criticized as incompatible with Western democracies is viewed by many as a dangerous shift.

The 70-year-old Corbyn's rise to the head of the country's second-most popular party was first viewed as a shocking ascent for a "backbench" politician whose views are considered far left of the conventional liberal agenda and a threat to global alliances.

"I'm loath to comment about people's elections in other parts of the world," Sen. Robert Menendez (D-N.J.), the ranking member of the Senate Foreign Relations Committee, told The Hill when asked about a potential Corbyn victory.

"However, when we have either a leader or a country that moves in an opposite direction from our core values, I always think that we should be free and powerful enough, and have a deep enough relationship, to express our differences when they exist. ... If that ends up being the case with Great Britain, I will," he said.

Corbyn has been criticized for extremist views against interventionism - condemned as supporting autocratic leaders in Iran, Venezuela and Cuba - and calling for the dismantling of NATO and breaking up Western alliances.

"His entire political career and worldview is guided by anti-Americanism, that's how he sees the world," said James Kirchick, author of "The End of Europe: Dictators, Demagogues, and the Coming Dark Age" and whose research focuses on rising antisemitism and populism in Europe.

"His ideological friends are Hamas and the Iranian regime. ... [Britain] is America's closest ally historically, and for it to be led by a man whose entire worldview is motivated by hatred of the United States, I think that's a really chilling prospect."

The "special relationship" between the U.S. and U.K. is considered one of the strongest bilateral alliances. The two countries are expected to negotiate new trade deals if Britain leaves the European Union as part of Brexit, the key issue that is forcing the country's record third elections in the past five years.

On top of that, the U.S. and U.K. are party to the "Five-Eyes" alliance of intelligence sharing, along with Australia, Canada and New Zealand.

A potential Corbyn premiership could jeopardize those ties and other sensitive intelligence relationships with countries like Israel.

The Labour leader has given his support for terrorist organizations like Lebanon's Hezbollah and Palestinian Hamas and has earlier stated that he would recognize an independent Palestinian state if elected.

Israeli Prime Minister Benjamin Netanyahu, in an interview with a British newspaper, signaled that Israel could downgrade intelligence sharing with Britain if Corbyn moved into 10 Downing Street. Corbyn has said he'd review British arms sales to Israel over its conflict with the Palestinians if elected prime minister.

"What do you think?" Netanyahu said in response to a question by the London Telegraph if Corbyn presents a challenge to security cooperation between the U.K. and Israel.

At least seven Labour members have resigned in protest of what they called growing anti-Semitism in the party, and the U.K.'s Chief Rabbi has accused Corbyn of "allowing a poison sanctioned from the top" to take hold.

Sen. Tim Kaine (D-Va.) said Labour's leaders should do more to combat anti-Semitism in its ranks.

"I am troubled by anti-Semitism in our country, in the U.K. and certainly understand why there's a great deal of concern," he said. "The recent statement by the leading rabbi in England about how Corbyn's statements have caused so many Jews in England to be concerned about Labour, people who are members of that party, leaders of that party, should take that very seriously."

Deadly anti-Semitic attacks in the U.S. - on a kosher supermarket in New Jersey and synagogues in California and Pennsylvania - underscore how people consumed by hatred toward Jews have grown more emboldened across the country, with American Jews largely blaming President Trump for encouraging such views.

The American Jewish Committee found that in a survey of U.S. Jews, more than half blamed a rise in anti-Semitism in the U.S. on rhetoric by the Republican Party.

In England, a recent survey by the Campaign Against Antisemitism and Kings College London found anti-Semitism on the political far-left was more dangerous than on the far-right, and that two-thirds of Corbyn's most loyal supporters hold at least one anti-Semitic view.

"I think criticisms [of Corbyn] are certainly legitimate," said Sen. Ben Cardin (D-Md).

"He needs to be condemned by the members of the Labour party as well as all individuals who understand that there can be no room for that type of language and that type of action anywhere, certainly U.K., which has been one of the leaders on human rights and democracy and tolerance. It's just outrageous."

Sen. Christopher Coons (D-Del.) said he would hope voters would reject parties that traffic in anti-Semitism but that populism and "widespread popular discontent" are "driving different or unexpected results."

"Of course, anti-Semitism in any form is reprehensible and should be rejected by voters of any country or party," he said.

Yet Coons is optimistic about the future of the U.S.-U.K. relationship, saying the alliance has survived past tensions. "I expect that relationship will remain very close."

Sen. Chris Murphy (D-Conn.), however, expressed concern over leadership on the U.S. side as one of the dangers to the close alliance with the British.

"I have concerns about the U.S. and U.K. relationship due to what President Trump has done to undermine it."