The leading Republican on the bipartisan Senate Gang of Eight says the group’s immigration bill will have to include stronger border security and enforcement measures if it is to pass the House of Representatives.

“I believe that the enforcement mechanisms in this bill, in order for the bill to pass in the House, will have to be strengthened,” Sen. Marco Rubio told radio host Hugh Hewitt on Tuesday. In another appearance, with host Mike Gallagher, Rubio said, “The bill that’s in place right now probably can’t pass the House. It will have to be adjusted, because people are very suspicious about the willingness of the government to enforce the laws now, given our experience with immigration in the past.”

Hewitt questioned Rubio specifically about the bill’s lack of any provision mandating the construction of more border fencing.  “If an amendment is brought forward mandating construction of a double sided fence over a specified length, and I think it ought to be at least half the border, a thousand miles or so, would you support such an amendment, Senator Rubio, that mandates it?”

“I’m fine with that,” Rubio said. “I personally, and I’ve consistently said this, I personally believe that double fencing is a very effective, not 100 percent, but a very, we’ve seen it be effective in the San Diego area and the Tijuana area, for example. So I personally am supportive of that. Others have different views about what would be more effective.”

Rubio’s “I’m fine with that” certainly suggests he would support a mandate for more fencing, but it also seemed a bit passive — that Rubio would not oppose such a measure if someone else pushed it. At another point in the program, Hewitt asked the question again. “Senator, just going back to what we covered, if an amendment comes forward that mandates construction of a double-sided fence over, say, a thousand miles … would you vote for that amendment?”

“Yeah, again, I mean, I don’t know if a thousand miles is the right number, but whatever that number is that wins people’s confidence, I’m for it,” Rubio said.

Rubio pointed out that Homeland Security Secretary Janet Napolitano doesn’t support more fencing. “I advocated for a specific pot of money in the bill set aside just for fencing,” Rubio told Hewitt. “And you heard how well advised that was, because just a couple of days ago, Janet Napolitano testified, and said she wants to get rid of that pot of money. She doesn’t want to have a fencing pot separate from the general spending. I think the fencing part is important. And I’d be more than happy to expand it to be the effective ring. As you said, there are parts of the border that do not need fencing, because it’s high mountain or it’s a river, or what have you. I’ll leave that to experts and others. But I can say to you that I believe that double fencing in the right places has been highly effective, especially, for example, in the San Diego area where it’s really been effective.”

Given those beliefs, it’s not clear whether Rubio pushed to include stronger fencing measures in the bill but was not able to win the support of other Gang members, or whether Rubio believes it is the responsibility of others to try to strengthen the bill’s security mandates. But there’s no doubt that one of the bill’s main architects believes it will have to have tougher security provisions if it is to become law.