Donald Trump puts Republican rival candidates on defensive, in vice presidential mode

With his popularity soaring after a weekend rally that drew more than 30,000 supporters, Donald Trump on Sunday took aim at President Obama, Democratic presidential front-runner Hillary Rodham Clinton and his own party rivals as he continued his unlikely ride atop the Republican presidential field.

The real estate mogul’s rise has left other Republican presidential candidates on the defensive on immigration and other issues, and some contenders are even publicly floating the notion of serving as Mr. Trump’s vice presidential candidate.

In an interview on ABC’s “This Week” program Sunday, Mr. Trump defended his plan to build an impenetrable wall separating the U.S. and Mexico, saying the Obama administration is unable to address the problem because of sheer incompetence.

“I’m going to get great people that know what they’re doing, not a bunch of political hacks that have no idea what they’re doing, appointed by President Obama, that doesn’t have a clue. I mean that man doesn’t have a clue,” Mr. Trump said. “People are walking across the border right now, right in front of these great people that we have. We have wonderful Border Patrol people. They can do their job, but they’re not allowed to do the job.”

He also took on Mrs. Clinton — who remains under siege for her use of private email while secretary of state — and Vice President Joseph R. Biden, who appears to be inching closer to entering the race. Mr. Trump said both are establishment politicians who do not represent what the American people are looking for.

“I think they’re the same. I think that Hillary may be very damaged because of the email thing,” he said. “But I don’t know. Assuming she could get over that, which I just don’t know how she possibly can, but if assuming she could, I would say it would be pretty equal.”

Mr. Trump made the comments two days after he drew more than 30,000 to a political rally in Mobile, Alabama, underscoring the support he has cultivated among conservatives.

Other Republicans now seem willing to attach themselves to Mr. Trump and may be gunning for the vice presidential nomination.

“I think all things are possible. But it’s much too early to begin such conversations,” retired neurosurgeon Ben Carson told CNN’s “State of the Union” Sunday after being asked whether he would serve as Mr. Trump’s No. 2.

Other Republican contenders now find themselves following Mr. Trump’s lead on key policy debates. Mr. Trump in recent weeks has voiced concern about the 14th Amendment, for example, which provides for birthright citizenship for anyone born in the U.S.

Mr. Trump has said the amendment must be changed to discourage illegal immigrants from using “anchor babies” to remain in the country. Other Republican presidential contenders also say the provision should be re-examined.

Wisconsin Gov. Scott Walker, one of Mr. Trump’s main challengers, said Sunday that the U.S. must crack down on illegal immigration, but he came out against changing the 14th Amendment.

“My point is, any discussion that goes beyond securing the border and enforcing the laws are things that should be a red flag to voters out there, who for years have heard lip service from politicians and are understandably angry because those politicians haven’t been committed to following through on those promises,” he told ABC News.

Mr. Trump also saved some of his fire for Mr. Walker, former Florida Gov. Jeb Bush and other Republican rivals.

He took direct aim at Mr. Walker’s economic record in Wisconsin.

“I love the people of Wisconsin, but if you look at what’s going on, they have a $2.2 billion deficit. They were supposed to have a surplus of $1 billion, and they have $2.2 billion. There’s tremendous divisions throughout the state,” he said.

As for Mr. Bush, Mr. Trump argues that he is “too soft” for the job of president.

“I don’t mind Jeb Bush. I think he’s a nice person. I just don’t think he has the energy. You need energy for this job. You can’t be soft,” he said. “And we need a person with a lot of smarts, a lot of cunning and a lot of energy. And Jeb doesn’t have that. I think he’s a very nice person. If he came president — if he became president, good luck. It’s another Bush. It’s going to be the same old story.”