Paul got the endorsement of fellow libertarian-leaning Republican Rep. Justin Amash (R-Mich.) (Ethan Miller/Getty Images)

GRAND RAPIDS, Mich. -- Rep. Justin Amash (R-Mich.) endorsed Sen. Rand Paul (R-Ky.) for president Monday.

The endorsement from Amash, who was an ally of Paul's father, Ron, was no surprise. Amash and Paul come from the same playbook: libertarian-leaning members of Congress who relish in being a thorn in the side of the establishment, are privacy advocates and are willing to lob bombs at their opponents.

"Rand Paul is a once-in-a generation sort of candidate," Amash said at the Kent County Republican Party headquarters here, where he appeared with Paul. Amash praised Paul's calls for a balanced budget and to stop government surveillance of phones and computers, and his attempts to broaden the Republican Party by courting young people and minorities.

"Rand Paul is the most electable candidate for president that we have," Amash said. "He's the one person who can unite our party and also bring new people into the party."

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Amash joins former congressman J.C. Watts, who introduced Paul at his campaign launch last month.

But Paul continues to poke at his Senate colleagues -- well, one in particular. For weeks, Paul and longtime adversary Sen. John McCain (R-Ariz.) have been tangling over their differing views on foreign policy. Paul swung back at McCain, who once labeled him and fellow presidential candidate Sen Ted Cruz (R-Tex.) "wacko birds."

Amash, Paul said, is part of the "next generation of liberty lovers" in Washington.

"I'd say he's a fellow wacko bird. Remember there was some old guy, I can't remember his name, who called us wacko birds," Paul said. "How wacky is it to be somebody who actually believes in the Constitution and all of the Bill of Rights?"

Paul never mentioned McCain by name but made abundantly clear who he was talking about.

"I won't tell you who it is, but it's a senator from Arizona," Paul said.

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Paul called for lower taxes -- a cry that has significance here in Michigan, which will vote Tuesday on whether to increase the state's sales tax to pay for road improvements. As he does on the campaign trail, Paul laid out a case for why Republicans must assert their support for all of the Amendments of the Constitution, not just the Second, the one he said Republicans are the most vocal about.

"10, 20, 30, however many are running for  president this year, whenever they come to Western Michigan they're all for the Second Amendment," he said. "It's not going to differentiate anybody."

Paul said he -- and Amash -- are different because they are advocates for privacy, criminal justice reform and due process. Paul spent much of his speech on privacy, an issue that rocketed himself and Amash to prominence, making the case that if the government has your phone or credit card records they know just about everything about you, from whether you drink or smoke to how you spend your time. When Paul mentioned the Fourth Amendment, a loud cheer went up.

"May the Fourth Amendment be with you," a man yelled, a reference to the date, May 4, and "Star Wars."

The justice system must be reformed, Paul said, because people can be falsely convicted.

"Amen!" someone yelled.

Paul pointed to the case of Richard Jewell, who was accused of the Atlanta Olympic bombings in 1996.

"If Richard Jewell had been a black man in south in the 1920s he wouldn't have lived the rest of the day," Paul said. He said he believes that 99 percent of police are "good people," but that police and judges are separated from one another so bias will not enter in.

"Bias because of color, because you're Jewish, or because you're an Evangelical Christian, or because you teach your kids at home. you can be a minority for a variety of reasons," he said.

As he always does, Paul wore his outsider label proudly, telling the audience that he beat back an establishment candidate when running for Senate in Kentucky and was fit for that office -- and the presidency -- precisely because he is not a career politician. While he is the scion of America's foremost libertarian family, Paul was an eye doctor before running for Congress.

The majority of laws, he said, are written by "unelected bureaucrats" and that bureaucracy and regulations have ballooned. Paul gets sustained bursts of applause on the campaign trail when he talks about cutting back on regulations and term limits for members of Congress; Monday he touted the REINS Act, which he sponsored and would  require that any regulation that would cost the country over $100 million would have to be voted on by Congress. But even Paul admits it likely won't go anywhere.

"This would be a huge step forward. We don't probably have the votes to pass it in the Senate .... but it would be a huge transformation of the way we do things up there."