ORONO, Maine — U.S. Sen. Ted Cruz told a raucous crowd on Friday at the University of Maine that he is the only Republican presidential candidate capable of beating Hillary Clinton, and he called on supporters of other GOP candidates to join him or risk sending Donald Trump to lose the election.

The senator from Texas blasted Republican front-runner Trump, who held a rally of his own on Thursday in Portland.

“For the 65 percent of Republicans across this country who recognize Donald Trump is not the best choice, [they believe] that Donald will lose to [Democrat] Hillary Clinton, and that will be a disaster for Republicans, a disaster for conservatives and a disaster for the country,” Cruz told members of the media in a dressing room before taking the stage.

“The only way to beat Donald Trump is for us to continue to unite and stand together,” he added.

Asked whether he would consider having U.S. Sen. Marco Rubio as a running mate, Cruz responded, “We are seeing discussions within the party about coming together. … There is no doubt, if we remain divided, Donald Trump wins. Remain divided — it is a path to catastrophe for this country.”

Cruz held his rally the day before Maine’s Republican Caucus, in front of more than 1,500 supporters and a smattering of protesters at the University of Maine’s Collins Center for the Arts.

He cast himself as the hardline Republican candidate who would not go back on his promises or compromise. Cruz contended that his main rival would back down on his campaign rhetoric if elected and cross the aisle to work with Democratic leadership, citing Trump’s use of the word “flexible” during a debate Thursday night. He also argued Trump would “cut a deal” with Democrats, bringing a liberal-leaning justice to the Supreme Court to replace the late Justice Antonin Scalia.

“I will not compromise away your religious liberties or your Second Amendment right to keep and bear arms,” Cruz said. “The Constitution and Bill of Rights are not up for negotiation.”

Cruz outlined several goals of his presidential bid — repealing “every word” of Obamacare, passing a “simple flat tax,” abolishing the IRS and cracking down on illegal immigration.

As of Friday, Trump had garnered support from 329 delegates, with Cruz trailing at 231, Rubio at 110, and John Kasich at 25. A candidate needs 1,237 delegates to secure the presidential nomination. Maine has 23 delegates at stake during its caucus on Saturday.

A few protesters and hecklers were scattered throughout the audience during the rally. One man held up a sign that read “No human beings are illegal” when Cruz began discussing immigration policy and border security.

Cruz stopped his speech, read the sign aloud, and said he agreed that all human beings are equal and created by God but said that doesn’t give them the right to violate immigration laws.

Police took signs but did not force protesters who held them up to leave. One man was escorted out after shouting out several times. Another walked out on his own after shouting about the importance of not ignoring global climate change.

Cruz, rather than asking security to escort out protesters, engaged them, usually by taking swipes at liberal college professors and students.

Another small group of protesters stood outside the Collins Center and debated calmly with Cruz supporters as they exited.

The venue was changed to the Collins Center the day before the rally. Originally, Cruz announced plans to speak in Hauck Auditorium on campus, which seats just 530.

Among the attendees at Friday’s rally was Clark Thompson, a 68-year-old Bangor resident who was born in Canada before being adopted by a family in Aroostook County.

Thompson is still trying to sort out which Republican candidate to throw his support behind. Thompson’s favorite is Ohio Gov. John Kasich, but he said he recognizes that Kasich doesn’t have the same backing and presence of other candidates. He also could see himself supporting Cruz, he said just before the candidate went on stage.

“From what I know, he’s honest, a straight shooter,” Thompson said. “I may not agree with a lot of his ideology, but I think he’s got some character about him.”

While Thompson calls himself an independent, he said he hasn’t voted for a Democrat in any recent federal election because of fiscally conservative leanings.

He said he’s fed up with the tone of this presidential race and that the debates and barbs traded haven’t been productive or informative for voters.

“I don’t remember a presidential election where there was so much of this name calling,” Thompson said. “It’s not presidential. It turns us all off.”

Follow Nick McCrea on Twitter at @nmccrea213.