Jeb Bush speaks at a pharmaceutical company in West Columbia, S.C., in late June. (Charles Ommanney/The Washington Post)

COLUMBIA, S.C. -- Republican presidential candidate Jeb Bush on Monday night dismissed as impractical Donald Trump's proposals to erect a U.S.-Mexico border wall, use remittances to pay for its construction and to revoke birthright citizenship.

"How do you revoke remittances?" he asked shaking his head. "A plan needs to be grounded in reality."

"I like my plan," he added in a one-on-one interview with The Washington Post.

The former Florida governor has written and said more about comprehensive immigration reform than any other presidential candidate of either party. A 300-page book he published in 2013 outlines in minute detail how the country could establish a path to earned legal status for the millions of undocumented immigrants living in the country while also revamping other elements of the nation's immigration system. Bush initially supported a pathway to citizenship for undocumented immigrants, but in recent years has shifted his focus to legalization.

Trump has unveiled a six-page plan that calls for tripling the number of law enforcement officers working along the Mexican border; deporting immigrants convicted of crimes; detaining and deporting immigrants caught crossing the border illegally; and erecting a wall along the southern border. Construction of the wall would be paid for by the Mexican government, or by revoking remittance payments sent back by Mexicans in the United States and increasing visa fees for Mexican businessmen and diplomats.

[With Trump's rise, hard-line immigration ideas take hold in GOP]

In his plan, Trump also calls for the end of birthright citizenship, a move designed to remove what he said is a major draw for undocumented immigrants crossing illegally into the country.

Bush hasn't reviewed the specifics of Trump's proposals and during the interview seemed unimpressed by what he'd already heard in press reports and from aides.

Republican presidential candidate Donald Trump released a detailed immigration plan, and its "great, great wall" is just the beginning. (Gillian Brockell/The Washington Post)

Revoking birthright citizenship would require a change to the Constitution, he noted. That's a lengthy process, so in the meantime, "There needs to be real efforts to deal with the abuse of these factories where people come in and have children to gain the citizenship for the children. But this is in the Constitution. The argument that it's not I don't think is the right view."

That was a veiled reference to comments made Monday by Wisconsin Gov. Scott Walker, who noted that in the early 1990s, Sen. Harry M. Reid (D-Nev.) introduced legislation that would have clarified the 14th Amendment of the Constitution and revoked birthright citizenship. Reid has since abandoned that position and become a leading proponent of comprehensive immigration reform.

"There are like 10 things I would change in the Constitution with a magic wand," Bush said. "But in the interim, we've got to control the border, we've got to enforce the rule of law, we've got to deal with extended stays on legal visas, we've got to have an e-Verify system that's verifiable, we've got to deal with sanctuary cities, we've got to forward-lean on the border. There's practical things that we can do to reduce the flow of illegal immigrants, which clearly is important to do."

That list of to-do items all come from Bush's book and the candidate regularly runs through his ideas when asked by voters on the campaign trail.

In crafting his immigration plans, Trump said that he consulted Sen. Jeff Sessions (R-Ala.) -- a vocal opponent of the 2013 bipartisan immigration reform plan that passed in the U.S. Senate. When asked, Bush didn't say whether Sessions's ideas merit serious consideration by Republicans.

"That's what we have campaigns about, sure, I don't expect everybody to agree with my views, but I think you need to really make sure that you can defend it and that its reality-based," he said. "On that level, I appreciate that [Trump] has a proposal."

Other presidential candidates gave Trump's plans mixed reviews on Monday. The campaign of Democratic candidate Hillary Rodham Clinton denounced Trump's ideas as "extreme anti-immigrant positions." Walker, who is losing ground to Trump in the critical state of Iowa, endorsed Trump's idea of a border wall and said that the United States should "absolutely" stop granting birthright citizenship. But Sen. Lindsey O. Graham (R-S.C.), a lead sponsor of the 2013 immigration bill, slammed Trump's ideas as "gibberish" and "nonsensical" because they could "kill the Republican Party."

[Scott Walker: The U.S. should 'absolutely' stop granting birthright citizenship]

Bush spent Monday campaigning in Charleston and Columbia in South Carolina as he unveiled a new plan that would privatize more services currently offered by the Department of Veterans Affairs. The candidate also met with a new veterans advisory group and picked up the endorsement of 12 recipients of the Medal of Honor, the nation's highest award for valor.

He appeared at a town hall meeting sponsored by Concerned Veterans of America, a group aligned with the Koch brothers' political network that also advocates for the privatization of many VA services. And once again Bush couldn't avoid questions about Trump.

The town hall moderator made reference to Trump's comments aired Sunday on NBC's "Meet the Press" that he takes his cues on military and national security in part from retired military leaders who appear frequently on television.

In response, Bush said he takes most of his military advice from "a really dedicated group of young policy men and women that are serving in the campaign."

"What I do is to give them the broadest possible access to the broadest number of people," he added. That's a reference to a 21-member advisory team of GOP foreign policy experts who once worked for his father's and brother's presidential administrations. The group includes former secretary of state James Baker, who worked for George H.W. Bush, and Paul Wolfowitz, who was George W. Bush's deputy defense secretary and a lead architect of the Iraq war.

"We have a system so we reach out as far as we can, doesn’t mean that everybody’s idea ends up in a policy initiative," Jeb Bush explained. "I'm not going to fall into the trap to say that I watch 'Meet the Press' and I get my foreign policy from that."

On Tuesday, Bush campaigns in Rock Hill, S.C. before traveling to Atlanta for a fundraiser. He appears in New Hampshire and Ohio later this week.