Why the Senate May Spend Billions More on Border Security

June 20, 2013— -- A bipartisan agreement to beef up the border security requirements in the Senate's immigration reform bill could help deliver the votes it needs to pass.

The deal is expected to be announced on Thursday, ABC News reported. And if it's found to be acceptable to enough Democrats and Republicans, that could represent a key moment in the push for immigration reform. Immigration reform is a top domestic priority for President Obama, and Latino and immigrant-rights groups have clamored for reform that legalizes undocumented immigrants for well over a decade.

The exact details of the proposal, crafted by Sens. John Hoeven (R-N.D.) and Bob Corker (R-Tenn.) remain unclear. But sources told ABC News that the so-called "border surge" will call for doubling of the size of the Border Patrol from its current force of 21,000. It also mandates the completion of the 700-mile border fence authorized by Congress in 2006.

Here's why this is a crucial moment for the bill:

Why We Are Considering More Border Security

We'll get to the policy reasons in a bit. But politically, the reason is that the bill's sponsors want more Republicans votes.

Authors of the legislation have said they want to get 70 votes in order to send it out of the Senate with a large enough majority to cajole the House of Representatives to act. With only 54 senators caucusing with Democrats, that would require getting 12 additional GOP votes (other than the four Republican co-authors of the bill).

In turn, Republican members have demanded that stricter border security measures be added to the bill in exchange for their votes.

But at least two other proposals have already been voted down in the Senate.

One of those, put forward by Sen. John Cornyn (R-Texas), has been labeled a "poison pill" by the bill's supporters. That proposal would require that the government have "operational control" of the border before most undocumented immigrants legalizing under the bill could obtain permanent status. If it was adopted, Democrats would have fled en masse and the bill likely would have died over concerns that it would block the path to citizenship.

The hope of the latest proposal is to bridge the gap between both sides. And there's already evidence that adopting the proposal could successfully bring on more Republican votes.

"This is dramatic improvement on border security that I hope will allow this legislation to have support it needs," Sen. Marco Rubio (R-Fla.), an author of the bill, said Thursday on Fox News.

Why We Don't Need More Border Security

The border security compromise might bring along more Republican votes in the Senate, but it could cause some Democrats to hold their nose as they vote for the bill.

Many Democrats, including President Obama, have repeatedly argued out that the U.S.-Mexico border is more secure than it has been in decades. The Wall Street Journal editorial board pointed out today that illegal entries are at a 40-year low. And the U.S. spent more on immigration enforcement ($18 billion) than all other federal law enforcement combined in 2012.

"All the talk-show shouting about America under siege from immigrants streaming across the Rio Grande is fiction," reads their editorial.

But the scope of the border measures in the new Republican proposal is unprecedented.