In 2013, Hillary Clinton announced her support for same-sex marriage in a Web video, saying "I support it personally, and as a matter of policy and law."

And with that video, Clinton ended what had at times seemed to be a tortured effort to find her stance on an issue that represents one of the largest and most rapid cultural changes in modern times.

Few politicians have been in the public eye longer than Hillary Clinton. In the nearly 25 years since her husband was elected president, her views have changed on many issues. Some accuse her of political opportunism, while Clinton's backers argue she has adapted as times and circumstances have changed.

Take gay marriage. Back in 2004, when Clinton was a senator from New York, she opposed a constitutional amendment banning gay marriage. However, in a speech on the Senate floor, she didn't stop there.

"I believe that marriage is not just a bond but a sacred bond between a man and a woman," she said.

As a presidential candidate in 2008, Clinton said she favored civil unions.

So what changed? Clinton argues America changed, right along with her own views.

"I think we have all evolved and it's been one of the fastest, most sweeping transformations," Clinton told Terry Gross on WHYY's Fresh Air in 2014.

In the first question of the first Democratic debate of this campaign cycle, CNN's Anderson Cooper confronted Clinton with a laundry list of issues where her position had shifted.

"Plenty of politicians evolve on issues, but even some Democrats believe you changed your positions based on political expediency," Cooper said before going into the list. "You were against same-sex marriage, now you're for it. You defended President Obama's immigration policies, now you say they're too harsh. You supported his trade deal dozens of times; you even called it the 'gold standard.' Now, suddenly last week, you're against it. Will you say anything to get elected?"

Clinton argued she has been consistent to her values but has adjusted her positions based on new information. When it comes to trade, Clinton's been all over the map. In 1996, she said, "Oh, I think that everybody is in favor of free and fair trade, and I think that NAFTA is proving its worth."

That would be the North American Free Trade Agreement, signed by President Bill Clinton.

Then in 2008, when she was running for president, Clinton said the U.S. should take timeouts from trade agreements and renegotiate NAFTA. But in 2011, as secretary of state in the Obama administration, Clinton praised the Trans-Pacific Partnership trade deal, which was being negotiated at the time.

"The TPP represents a new kind of trade agreement, one that promotes, not just more growth, but better growth," Clinton said at a conference of Asian nations.

Her tune changed last year, a week before the first Democratic debate. TPP negotiations had just been completed when Clinton sat down with Judy Woodruff on the PBS NewsHour.

"Are you saying that, as of today, this is not something you could support?" asked Woodruff. "What I know about it, as of today, I am not in favor of what I have learned about it," Clinton replied, making news after she had spent months refusing to take a position on TPP.

Some of Clinton's policy positions were first staked out when her husband was president or when she was secretary of state under President Obama. At times, it wasn't entirely clear whether she was talking about her own views or promoting those of the presidents.

Clinton praised the crime bill in the 1990s for getting more cops on the beat.

"That was one of the goals that the president had when he pushed the crime bill that was passed in 1994," said Clinton. "He promised a hundred thousand police. We're moving in that direction."

But her first major policy speech of this campaign was about criminal justice reform, including reversing the mass incarceration many blame the crime bill for accelerating. Clinton was asked about what changed in a CNN debate earlier this year.

"We both supported it," Clinton said, pointing out that Bernie Sanders had actually voted for the crime bill. "And I think it's fair to say we did because back then there was an outcry over the rising crime rate and people from all communities were asking that action be taken."

There are issues where Clinton's positions have changed faster than on crime, trade or marriage. Over the course of five years, she went from being "inclined" to support the Keystone XL pipeline, to refusing to express a position, to opposing it in 2015 while running for the Democratic nomination.

Clinton's 2002 vote to authorize the war in Iraq has dogged her through two presidential campaigns now. In 2008, it was one of the most potent attacks from Barack Obama, and Clinton defended the vote, though she said that if she knew what President George W. Bush did with that authority she wouldn't have given it. Clinton has later said she also didn't want to make the troops fighting in Iraq in 2008 to feel as if their mission was a mistake.

By the time Clinton declared that she would run again in 2016, she had written in her 2014 book Hard Choices: "I got it wrong. Plain and simple."

In the primary, Sanders has used Iraq as a contrast like Obama did before, but Sanders actually cast a vote on the authorization for war as a member of the House. He voted no.

Sanders has benefited in this campaign from a larger contrast with Clinton's evolutions. He's been talking about his core issues — particularly income inequality — in essentially the same way for 40 years. But Democratic pollster Margie Omero isn't convinced shifting with the times is always a bad thing for a candidate.

"There are a lot of issues where the public has moved and so it's reasonable for our elected leaders to move," said Omero. But for some candidates, she added, it is a problem.

"The challenge is when movements on an issue support a narrative that already exists," said Omero.

Already Clinton's GOP opponents are working to set a narrative, to make sure voters ask themselves whether her shifts mean Clinton can't be trusted or doesn't have the courage of her convictions. And Clinton's 25 years of public life give them lots of material.

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