On Saturday, former Maryland Gov. Martin O'Malley announced he's running for president. O'Malley is the third Democrat to launch a campaign and will face-off against front-runner Hillary Clinton and Sen. Bernie Sanders (I-Vt.) for the Democratic nomination.

O'Malley got his start in Baltimore, where he served as mayor. He then served two terms as governor of Maryland; his second term ended in January of 2015. A generally moderate Democrat, O'Malley spent the end of his governorship bolstering his liberal credentials, including raising the minimum wage to $10.10 and pushing for the legalization of same-sex marriage.

Here is where O'Malley stands on five key issues for Millennials: marijuana, higher education, LGBT rights, the environment, and immigration.

1. College costs and student debt.

Prior to leaving the governor's office, he proposed a $40 million dollar cut to Maryland's public higher education system (which prompted the University of Maryland system to announce a mid-year tuition bump.) Before those cuts, however, O'Malley received high marks from the Maryland Higher Education Committee for his work on higher ed. Some of these accomplishments included a tuition freeze (which began in 2006 and ended in 2010) and more than $333 million in his budgets for grants and scholarships during his first three years in office. In 2007, he also created the Higher Education Investment Fund and proposed Complete College Maryland, which were incentives to finish college on time.

In terms of student loans, O'Malley wrote an op-ed in the Washington Post in April 2015 discussing his plans to deal with student loan debt:

"First, Congress must allow students to refinance the debt they have. Unlike homeowners or businesses, student borrowers can’t refinance their loans to take advantage of lower interest rates.

"This is outrageous. If we were able to bail out big banks, we can figure out a way to refinance college loans."

His other plan calls for monthly caps on what students can pay so they don't default or go further into debt to pay off loans.

2. Marijuana.

Unlike other candidates, as governor (along with a cooperative state legislature) O'Malley was able to institute some marijuana legislation. In April 2014, he signed a bill to decriminalize small amounts of marijuana: those caught with less than 10 grams would receive civil fines and not face criminal punishment.

"As a young prosecutor, I once thought that decriminalizing the possession of marijuana might undermine the public will necessary to combat drug violence and improve public safety,” O'Malley stated in a release at the time. "I now think that [it] is an acknowledgment of the low priority that our courts, our prosecutors, our police and the vast majority of citizens already attach to this transgression of public order and public health."

O'Malley, who was a criminal prosecutor before becoming mayor of Baltimore, built a "tough on crime" reputation -- a policy that has fallen out of favor and may have contributed to policing problems in Baltimore.

As of January 2014, O'Malley was not in favor of legalizing marijuana for recreational use. He told CNN's Candy Crowley the following on "State of the Union":

O'MALLEY: I'm opposed to it for a number of reasons.

O'MALLEY: I mean, in our state, I actually have signed legislation that allows police officers to issue citations instead of arrests. We've made a, you know, a mandatory stay and a right of appeal to anybody that's, you know, subjected to any sort of incarceration.

So I think there is something to be said for the proportionality. And I do think that all of that is important. There are fewer people incarcerated in Maryland today than when I was elected.

But for a number of reasons -- you know, one of them, Candy, is purely economic. In our state, a lot of the new opportunities that are opening up for our kids in security and cyber security and other things, they require a background check and they require that kids have clean records and the best...

CROWLEY: But if you legalized it, there wouldn't be a record.

O'MALLEY: Yes, but we can't do that as a state. That would be something only the nation could do. And for us to go down that direction as a single state, I mean I don't...

CROWLEY: Well, Colorado has.

O'MALLEY: Colorado has.

CROWLEY: (INAUDIBLE) legalized...

O'MALLEY: Yes, Colorado has.

CROWLEY: Yes.

O'MALLEY: And for Colorado...

CROWLEY: Yes.

O'MALLEY: -- perhaps that's a good choice and perhaps there's things we can learn from their experiment as a laboratory in democracy.

From Maryland's standpoint, I spend a lot of time in middle schools telling kids to keep a clean record so that they can get a good job and help their families.

The video of the interview is below:

3. Immigration

Martin O'Malley has received praise for his record on immigration from reform advocates.

In 2014, Rep. Luis Gutiérrez (D-Ill.) called O'Malley a "champion" of immigration. O'Malley signed laws making DREAMers, undocumented immigrants who were brought to the U.S. as children, eligible for in-state tuition and drivers licenses. During the refugee crisis at the border during the summer of 2014, O'Malley criticized President Obama for deporting the Central American children and their families back to countries plagued with violence.

"Martin O'Malley, in his history as governor of Maryland, has been a real hero for the immigrant community," Kim Propeack, chief of political communication for CASA de Maryland, told NBC News. "He not only supported many groundbreaking reforms in the state, he also became a national spokesperson for immigrant families and their human rights, especially the unaccompanied minors who arrived in droves on the border last year."

​4. LGBT rights

When O'Malley ran for governor, he ran as an advocate for civil unions. When in office, however, he proposed, supported, and eventually signed a bill that led to legal same-sex marriage in Maryland beginning on January 1, 2013. Here's Martin O'Malley discussing same-sex marriage with the Des Moines Register:

In 2014, Martin O'Malley signed a law banning discrimination against transgender Marylanders, joining D.C. and 17 other states with laws protecting the transgender community from discrimination.

5. The environment.

O'Malley has a strong, pro-environment record. Grist calls him a "climate hawk" and published a great profile on O'Malley's environmental action as governor.

So what does being a "climate hawk" entail? In 2006, he signed a law aimed at reducing Maryland's carbon emissions by 25 percent from 2006 levels by 2020 and created ClimateStat, a program with quarterly meetings to monitor the reduction. O'Malley also focused on projects like cleaning up the Chesapeake Bay, planting more trees on both public and private land, adopting the Clean Cars Act, and expanding public transit.

Also, according to Grist, he has the trust of Maryland environmental activists.

“I deal with a lot of politicians in my work as a climate advocate,” Director of the Chesapeake Climate Action Network, Mike Tidwell, told Grist. “Martin O’Malley, more than any politician I know, really loses sleep over climate change. He is deeply concerned about climate change and his actions over the last eight years reveal that. He’s pushed the envelope more than anyone I’ve seen."

O'Malley's pitfalls include proposing a trash-to-energy program in the majority African American city of Baltimore, upsetting environmental justice activists, who point out that it would worsen already polluted air. At the end of his time in office, O'Malley also allowed limited fracking, but some see that as a preemptive measure to implement strict fracking regulations prior to a pro-fracking governor coming into office. (That Republican, it turns out, is okay with a recently passed fracking ban in the state.) Environmentalists were also frustrated with the delayed action on reducing phosphorous runoff into the bay. "The rules were intended to limit how much chicken manure farmers may use as fertilizer," the Baltimore Sun explains. "When it rains, the runoff washes phosphorus into the bay." These rules didn't go into effect until the very end of his term.

You can register to vote for the 2016 election at OurTime.org.