Republican presidential candidate Mitt Romney refused to endorse Florida Senator and prospective running-mate Marco Rubio's DREAM Act GOP alternative proposal that would allow young undocumented immigrants to remain in the United States to work or study. Though Romney passed on supporting the proposed measure, he added that there were provisions to "commend" in it and that his campaign would "study the issue."  

The questions on immigration came as Romeny and Rubio were on the campaign trail together in Pennsylvania, on Monday, a day before the state's primary.

Rubio's still-evolving bill would allow young undocumented immigrants who graduated from high school and have no criminal record to obtain a nonimmigrant visa. They could stay in the United States, obtain a drivers' license and work or continued their studies but would have no special path to citizenship.  Rubio has said his goal is to craft a Republican compromise on the so-called DREAM Act in time for the upcoming Fall semester that Romney could support. 

I anticipate before the November election we'll be laying out whole series of policies that relate to immigration, and obviously our first priority is to secure the border...

- Mitt Romney, Republican Presidential Candidate

The DREAM Act, which has languished on Capitol Hill, would provide a path to citizenship for some young undocumented immigrants who attend college or serve in the military.

It appears Rubio has more work to do for that endorsement as Romney wouldn't go so far as to embrace Rubio's immigration proposal. 

Romney said during the South Carolina primary that all undocumented immigrants should return to their home country and get in line to be eligible for U.S. citizenship.

The former Massachusetts governor's answers illustrate the careful line he has to walk as he transitions from the primary to the general election, where he'll have to tussle with President Barack Obama for support from the Latino, female and young voters who propelled Obama to victory in 2008.

Obama, meanwhile, has to hang on to those constituencies. His tour through North Carolina, Colorado and Iowa on Tuesday and Wednesday is intended to rally young supporters.

Romney tacked to the right on immigration during the primary but in recent days, he's been highlighting Latino concerns at events while leaving out much of the rhetoric he embraced earlier this year. He said Monday that he would outline additional changes to the immigration system in the coming months, particularly with the visa system that governs who is allowed to work in the U.S.

"I anticipate before the November election we'll be laying out whole series of policies that relate to immigration, and obviously our first priority is to secure the border, and yet we also have very substantial visa programs in this country," Romney said. "How we adjust our visa program to make it fit the needs of our country is something I'll be speaking about down the road."

The Cuban-American senator is considered a top potential pick for vice president. He's the latest in a string of possible running mates to campaign with Romney and is the first to get an audition since former Sen. Rick Santorum, R-Pa., left the race and Romney staffers formally began organizing the process of searching for a No. 2.

Romney declined Monday to say if Rubio was on his list of vice presidential candidates. He said his campaign is still setting up the infrastructure that's required to scrutinize potential nominees, including hiring legal and accounting staff.

The former Massachusetts governor also refused to say whether Rubio is experienced enough to serve as his No. 2. Romney often criticizes Obama, who was a first-term senator when he was elected president, as a "nice guy" who is "in over his head," implying that the Democratic incumbent didn't have the experience he needed for the job.

Meanwhile, Romney embraced a student loan proposal that Obama is selling on the campaign trail.

The policy position signaled an effort by Romney to move to the political center as he works to court critical general election swing voters — including young voters and Hispanic voters — after a brutal primary fight.

"I think young voters in this country have to vote for me if they're really thinking of what's in the best interest of the country and what's in their personal best interest," Romney said as he stood next to Rubio, R-Fla.

Romney answered reporters' questions for the first time since effectively securing the GOP presidential nomination.

Romney's language on loans was distinctly different from the answer he gave when he was last asked about the issue. Prior to the Illinois primary on March 20, he told a young woman concerned about student debt to "get ready for President Obama's claim."

"I know he's going to come up at some point and talk about how he's going to make it vanish. And that's another, 'Here, I'll give you something for free.' And I'm not going to do that," Romney said. During that same answer, he said he wanted to keep interest rates low.

House Republicans have said the estimated $6 billion annual cost of extending low-interest rates for student loans isn't affordable without offsetting cuts but that they are still deciding whether to support a temporary extension. Obama has started pushing Congress for the extension and planned a three-state tour this week to warn students of the potential financial catastrophe they will face if Congress fails to act.

Interest rates are set to double on July 1, from 3.4 percent to 6.8 percent, on a popular federal loan for low- and middle-income undergraduates.

"I support extending the temporary relief on interest rates for students," Romney said Monday, a day before five states hold primaries, though he did not offer specifics on how the extension should be paid for or how long it should last. He said he supports the extension because of "extraordinarily poor conditions in the job market."

Based on reporting by the Associated Press.

Follow us on twitter.com/foxnewslatino
Like us at facebook.com/foxnewslatino