In April, presumptive Republican nominee Mitt Romney warned the National Rifle Association about the dangers of a second term of President Barack Obama and what it could mean for their Second Amendment rights. He said that Obama would be "unrestrained" in a second term, cautioning NRA members of the implications of who Obama could appoint to the Supreme Court.

But during his political career, Romney clashed with the NRA during separate runs for U.S. Senate and governor in Massachusetts. In fact, Romney was a prominent Republican voice for gun control, and even limited the use of assault weapons while governor of Massachusetts.

In the wake of the Colorado movie theater shooting last Friday, some politicians and advocates have renewed the call for the candidates to define where they stand on gun control. As Romney's speech to the NRA this year indicates, the Republican presidential candidate has hardened his position on gun rights since taking the national stage.

The flip-flop was prominent fodder for Romney's Republican opponents in both the 2008 and 2012 presidential primaries. Opposition research for Sen. John McCain's 2008 campaign, obtained by BuzzFeed, cites Romney's 1994 run for a U.S. Senate seat in Massachusetts against Sen. Ted Kennedy, during which Romney took a stance that put him at odds with the NRA — and insisted that he didn't care.

The memo cites this passage, from a 1994 Boston Herald article:

"I don't want special interest groups making this their campaign," he said then. "I don't want their money. I don't want their help. This is my race." Romney would be a likely recipient of contributions and support from an array of national servative groups long aligned against Kennedy, the Senate's leading liberal voice.

But the GOP nominee said he will take stands that put him at odds with some traditional ultra-conservative groups, and cited his support for the assault rifle ban and the Brady gun control law.

"That's not going to make me the hero of the NRA (National Rifle Association)," he said. "I don't line up with a lot of special interest groups."

Later, as governor in 2004, Romney signed a permanent assault weapons ban into law in Massachusetts. That included guns like the AR-15, which was one of the weapons used by suspected gunman James Holmes in the Colorado theater shooting.

“I believe the people should have the right to bear arms, but I don’t believe that we have to have assault weapons as part of our personal arsenal,” he said on Fox News in 2004.

But in 2006, when Romney was planting the seeds for a run for president, he began to walk back on some of the hard-line positions he took on gun ownership in Massachusetts. First, he joined the NRA as a designated "Lifetime Member." And in 2007, he told a crowd in New Hampshire, plainly, that he wanted the NRA's endorsement.

"I'm after the NRA's endorsement. I'm not sure they'll give it to me. I hope they will. I also joined because if I'm going to ask for their endorsement, they're going to ask for mine."

Today, Romney's campaign website suggests that Congress does not need to revisit the assault weapons ban. His campaign website highlights legislation that "expanded the rights" of gun owners that Romney signed while he was governor, but does not mention the assault weapons ban:

Like the majority of Americans, Mitt does not believe that the United States needs additional laws that restrict the Second Amendment right to keep and bear arms. He believes in the safe and responsible ownership and use of firearms and the right to lawfully manufacture and sell firearms and ammunition. He also recognizes the extraordinary number of jobs and other economic benefits that are produced by hunting, recreational shooting, and the firearms and ammunition industry, not the least of which is to fund wildlife and habitat conservation.