HARRISBURG, Pa. — A Republican running for the U.S. Senate in Pennsylvania is escalating criticism of Democrats over the Israel-Hamas war and has traveled to the Israel-Gaza border to make the case that the Biden administration hasn’t backed Israel strongly enough since the Oct. 7 attack by Hamas.

The criticism by GOP candidate David McCormick reflects the delicate political challenge facing both President Joe Biden and incumbent Democratic Sen. Bob Casey in a state Democrats can’t afford to lose in 2024.

Biden, who is seeking a second term as president, has been criticized from the left for being too pro-Israel in his response to its war on Hamas and for not doing enough to address the burgeoning humanitarian crisis among Palestinians in Gaza.

McCormick’s attacks echo those voiced on the GOP’s presidential campaign trail where candidates have portrayed Biden’s policy on Iran — a key financial backer of Hamas — as too weak to frighten what the U.S. calls the world’s leading state sponsor of terrorism.

McCormick said the U.S. should impose sanctions to cut off Iran’s oil sales and mount a more muscular response to attacks on U.S. targets in the Middle East to restore an order upended by what he called Biden administration mistakes going back to an incompetent withdrawal from Afghanistan.

“The key to America’s role in the world is peace through strength,” McCormick said in an interview Thursday. “And so I think what we’re seeing is the failure of deterrence. I think what we’re seeing is a belief, across the world, among our adversaries, that America’s a little flat-footed. America’s weak.”

Neither Casey nor McCormick are likely to face serious opposition in Pennsylvania’s April 23 primary before facing off against each other in November’s general election.

McCormick’s focus on the issue comes as a barrage of U.S., coalition and militant attacks in the Middle East are compounding U.S. fears that Israel’s war on Hamas in Gaza could expand.

The Biden administration’s support for Israel has been complicated politically in other states the president is counting on in his reelection bid. In Michigan, for example, Democrats worry that losing support among the state’s large Arab-American population over the war could damage their prospects. Michigan also has an open Senate seat on the ballot this year.

Pennsylvania and Michigan, along with Wisconsin, are indispensable parts of a “ blue wall ” of Rust Belt states that helped Biden defeat former President Donald Trump in 2020 after Trump won those states in 2016.

In the Senate, Democrats maintain a narrow majority, one that became more perilous late last year with the retirement of West Virginia Sen. Joe Manchin. That makes Casey’s seat even more pivotal to his party’s efforts to maintain control of the chamber.

McCormick’s effort to highlight his support for Israel is unique thus far in this year’s high-profile Senate contests, and it could become a test case for Republicans in fall general election contests.

McCormick hopes to peel off not only swing voters in Pennsylvania, but also members of the state’s relatively large Jewish community who vote predominantly Democratic — but could make a difference in a close election.

Even though the war has divided both Democrats and Jews, taking votes from Casey poses a formidable challenge. The incumbent senator is well-regarded by Pennsylvania’s Jewish community and has been a reliable ally in Congress for Israel and its fight against Hamas.

Vowing solidarity with Israel, McCormick took a two-day trip to Israel where he visited a kibbutz that was attacked by Hamas and met with government officials, hostage families and survivors of the Oct. 7 attacks.

McCormick, a former hedge fund CEO, told reporters that the fight against Hamas is between “the West versus evil.” He followed the trip with a media blitz and a letter to what his campaign said were tens of thousands of “persuadable” voters in Pennsylvania.

In the letter, McCormick quotes an orthodox rabbi known for his outreach to secular Jews and the Jewish scholar Hillel.

“Israel needs America’s firm and unequivocal support,” McCormick wrote. “Hamas must be destroyed. The lesson of October 7 is clear — the Middle East respects strength and that is why Israel must win. America’s mission must be to help Israel win. It’s that simple.”

McCormick did not mention Casey in the two-page letter. But he separately accused Casey and Biden of “appeasement” of Iran, going back to what he called the “original sin” of Casey’s support for the Iran nuclear deal under President Barack Obama in 2015 that critics say gave Iran the cash it needed to fund terror.

Casey countered that he has fought for years to back Israel in its fight against Hamas and that the Iran nuclear deal had been working — until Trump withdrew the U.S. from the agreement.

“That’s the type of reckless policy my opponent supports,” Casey said in a statement.

On policy, Casey’s and McCormick’s positions on Israel have a lot in common.

They both support military aid to Israel, backing Israel’s mission to destroy Hamas and putting aside allegations of Israeli war crimes, saying they are convinced Israel has gone to great lengths to avoid civilian casualties.

Both have slammed the savagery of the Hamas attack, and accused it of using civilians as human shields. Arab nations that publicly criticize Israel’s counterattack on Gaza privately tell their Israeli, U.S. and European counterparts that they want Hamas gone, Casey said on CBS News’ podcast “The Takeout.”

“They’re all saying, ‘please take out Hamas,’” Casey said.

Casey has not joined some of his Democratic colleagues in calling for a ceasefire, putting conditions on U.S. military aid to Israel or criticizing Israel for a bombing campaign that the the Hamas-controlled government says has killed more than 24,000 Palestinians. He also has not echoed Biden administration unease over the scale of Israel’s military operation.

Casey, running for a fourth-term, is endorsed by the fundraising powerhouse, the American Israel Public Affairs Committee, or AIPAC, and the former chairman of a Foreign Relations subcommittee on the Middle East has visited Israel six times over his 17-year Senate career.

In recent days and weeks, Casey visited a Jewish Community Center in Pittsburgh, attended the “March for Israel” on Washington’s National Mall and spoke at a synagogue in Philadelphia to denounce antisemitism.

For McCormick, foreign policy is a strength of his and a cornerstone of his campaign, something of a rarity in the current era. The decorated Army veteran held senior posts in the administration of President George W. Bush, including deputy national security adviser for international economic policy, and served on a defense policy board under Trump.

Republicans see Pennsylvania as a battleground state with a significant enough Jewish population — around 400,000, by their estimate — to swing an election decided by tens of thousands of votes.

For Jewish voters, Israel is not the only issue they care about, but it is a higher priority after the attack by Hamas, said Christopher Borick, director of the Muhlenberg College Institute of Public Opinion in Allentown.

Jewish voters typically vote overwhelmingly Democratic, and Democrats right now are trying to balance their interest in protecting Israel with that of younger voters, who have been sympathetic to Palestinians, he said.

“That’s something, of course, Democrats have to address in keeping their coalition together,” Borick said. “Jewish voters have been one of their most loyal supporter groups. Although not a gigantic segment of the population, it’s nonetheless crucial given the nature of tight elections in Pennsylvania.”