Washington CNN  — 

Sen. Lindsey Graham may be languishing in the bottom of GOP presidential primary polls, but on Thursday he delivered a sharp rebuke of his GOP opponents before a Republican Jewish audience.

“The one thing I can tell you is that what Mr. Trump’s saying about how to handle this war is empowering the enemy,” Graham said, referring to GOP front-runner Donald Trump’s recent assertion that the U.S. should “go after” the families of terrorists.

“ISIL loves Donald Trump because he is giving them an opportunity to bring people their way,” Graham said during a gathering with reporters following his formal speech to the Republican Jewish Coalition.

Also among the digs: He guaranteed that Republicans will lose the race for the White House if they nominate his opponents like Donald Trump and Sen. Ted Cruz.

The South Carolinian spoke just after the Texas Republican senator, and declared himself so frustrated with Cruz’s speech that he deviated from his prepared remarks.

“Not the speech you thought you were going to hear, right?” he said. “Not the speech I thought I was going to give.”

Graham launched into an attack on Cruz and Trump right from the top of his remarks, not starting with the San Bernardino shootings the day before as most candidates did.

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He took issue with Cruz’s preceding remarks that Republicans need to vote in strength, and low turnout is why the party failed to win in 2008 and 2012.

“How many of you believe we’re losing elections because we’re not hard-ass enough on immigration?’ Graham asked the crowd, to light applause. “Well, I don’t agree with you.

He said the party is losing Hispanic voters and women, and needs to be more practical about who it elects as its candidate for president.

“I think Donald Trump is destroying the Republican Party,” Graham said, to a smattering of applause.

Trump is leading the field at nearly 30% in most polls – Graham rarely hits the 1% mark in polling.

Graham appealed to the Jewish Republican crowd – which tends to be more moderate on social issues and focused on supporting Israel and tough foreign policy.

He compared his opponents’ rhetoric on illegal immigration to the Holocaust.

“Now it’s not self-deportation, it’s forced deportation,” he said, referring to Mitt Romney’s much-assailed position in 2012. “We’re literally going to round them up – That sound familiar to you?”

He continued: “You think you’re going to win an election with that kind of garbage –undercut everything you’ve worked for?”

He also knocked Cruz and Florida Sen. Marco Rubio for supporting banning abortion even in cases of rape or incest, saying the party will lose young women “in droves” with that position.

And Graham mocked Cruz’s stump speech line about the Obama administration fighting a group on nuns in the courts over its contraceptive mandate, saying the general election will become about the rape exception, instead.

“You really want to win this election? Start taking everything that we say seriously and push back when we make absolutely no sense,” Graham implored. “After Mr. Cruz, I’m going to talk to you about winning an election.”

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He did mention foreign policy, which the crowd expects to hear in heavy amounts from the entire field on Thursday. But he got a strongly positive reaction from the crowd in citing his extensive track record as a foreign policy hawk.

“Want to talk a little bit about foreign policy?” he said. “Do you even think I need to talk about you about my support for Israel?”

Amid the applause, some audience members could be heard saying “No.”

He asked the crowd to help Graham “stay in this race” so that he can be a voice of reason.

“You know how you win this election? You don’t lose it,” he said.

All the GOP candidates are speaking at the forum on Thursday.

CNN’s Ashley Killough contributed to this report.