If there's any liberal priority that's gone ignored by Maryland Gov. Martin O'Malley (D), I can't think of it. In his eight years in office, O'Malley has checked off one progressive policy goal after another: Legalize gay marriage, eliminate the death penalty, discount tuition for illegal immigrant students, impose new restrictions on guns, clean up the Chesapeake Bay, expand pre-kindergarten, promote wind power, ban discrimination against transgendered people, invest in education, raise the minimum wage to $10.10, and decriminalize possession of small amounts of marijuana.

That record ought to make him a viable contender for the Democratic presidential nomination, right? (With the usual asterisk that if she runs, Hillary Clinton would have a crushing advantage and could clear the field.)

But geography could get in the way. This all happened in Maryland — not exactly a bastion of Tea Party conservatives bent on blocking a Democratic chief executive at every turn.

While some of O'Malley's fellow Maryland Democrats aren't as liberal as he is, there's no denying the state's overwhelmingly blue cast. In the past 70 years, voters there have chosen only three Republican governors and six Republican presidential candidates. The Maryland Senate and House of Delegates have been controlled by Democrats since 1992. They currently outnumber Republicans 3 to 1 in the Senate and more than 2 to 1 in the House.

The disparity has helped O'Malley build a long list of achievements popular with Democrats. That's not to say any Democrat could have done what O'Malley did, but you can easily see how his potential 2016 primary rivals might use his blue-state advantage to chip away at his many accomplishments. After all, the public likes politicians who work across the aisle, and some Democratic presidential prospects have already demonstrated they can operate in divisive partisan settings — Clinton and New York Gov. Andrew Cuomo among them.

Both O'Malley and the man who hopes to succeed him, Lt. Gov. Anthony Brown, make a point of noting how many years it takes to get some of these bills through a Democratic legislature; in particular, Senate President Thomas V. "Mike" Miller opposed repeal of the death penalty. But the scale of conflict is relatively minuscule. The major disagreements over a minimum wage hike, for instance, were how high and how fast — not whether to raise it at all. The top irreconcilable difference among Democrats, still unresolved, was over how much money to give House of Cards to continue production in the state.

Any governor stymied by an opposition party, such as Terry McAuliffe, currently in a standoff with the GOP over expanding Medicaid in Virginia, might have envied those debates and the single-party tableau at an O'Malley bill signing Tuesday: governor, lieutenant governor, House speaker, and Senate president, all Democrats.

A standard promise in presidential campaigns is that a candidate will reach out to the opposition, work across the aisle, promote compromise to do the work of the nation. George W. Bush ran as "a uniter, not a divider." Barack Obama said there was no red America or blue America, just the United States of America. John McCain ran in 2008 on a bipartisan political reform platform. Mitt Romney said it was important to "find common ground" to move ahead. All four had records of working with the opposite party.

Clinton established the same in the Senate, where she sponsored scores of bills with GOP partners, and as secretary of state, where her Republican allies included Defense Secretary Robert Gates. Cuomo has made progress on gun control and gay marriage despite a closely divided state Senate, and has won GOP praise for holding the line on taxes and spending.

When Gallup asked voters last fall whether political leaders should compromise or stick to their beliefs, compromise won in a landslide — 53 percent to 25 percent. Sen. Johnny Isakson (R-Ga.) encountered this phenomenon on a visit home in December, shortly before Congress momentarily escaped gridlock to approve a two-year bipartisan budget agreement. He said he was approached by people he knew and didn't know, all across the political spectrum, at church, at a shopping mall, at the airport, and even at a dinner party with partisan activists, and the sentiment was universal: "Finally, you guys have gotten your act together."

O'Malley is a polished and aggressive partisan, having honed his message as head of the Democratic Governors Association, as a party spokesman on TV, and on the circuit at Democratic dinners and campaign events across the country. If he runs, he will have a strong substantive case to put before primary voters. He'll have more of a challenge convincing them he has what it takes to make headway in a less hospitable environment than Maryland. It's not his only potential obstacle, but it could well be a top consideration for some voters, given the despair-inducing dysfunction of the last few years.