DOVER — Delaware is largely a Democratic state. It has voted for the Democratic presidential candidate in the past six elections, it has not had a Republican governor since 1992, and both chambers of the General Assembly are controlled by Democrats.

That’s a lot of blue.

But even with nearly all legislative districts having more registered Democrats than Republicans, there are pockets of conservatism.

Take the 2012 presidential election. New Castle County went for Barack Obama in large numbers — he won 66.3 percent of the vote there. The middle county, Kent, saw the president garner 51.8 percent, while in Sussex County just 42.9 percent of voters backed the Democratic nominee.

New Castle, by far the most populous county, is solidly Democratic and contains the districts with the greatest Democrat-to-Republican ratio, in sharp contrast to Sussex.

That ideology does not cover all of New Castle County, however. Greenville, one of the wealthiest areas in the state, is represented by Republicans in both chambers. Not even the presence of Vice President Joe Biden’s household is enough to sway voters.

Aside from that, virtually all of the districts above the Chesapeake and Delaware Canal, one of the state’s traditional dividing lines, sent a Democrat to the legislature in the most recent election. While that area makes up less than one-third of the state in size, it contains the majority of the population.

Thirty-four of the state’s 62 legislative districts sit above the canal. Twenty-nine are represented by Democratic lawmakers.

Below the canal, districts are larger, with many capable of covering the entire Wilmington area with ease. They are also much more conservative.

Aside from a Middletown representative district, a senatorial district that stretches down from the canal, a cluster of blue around Dover and the lone bastion of the Rehoboth Beach representative district, all of Kent and Sussex’s districts are currently represented in the General Assembly by Republicans.

Setting aside three districts that overlap counties, New Castle has 36 areas represented in the General Assembly, Kent has 10 and Sussex has 13.

In that way, Delaware is a microcosm of the East Coast. The north is solidly Democratic and densely populated, the middle is more mixed and the south is strongly Republican.

Given all that, it’s no surprise, then, that two lobbying organizations say nearly all of most left-leaning members of the General Assembly come from New Castle.

The Delaware chapter of Americans for Democratic Action, which leans left, and American Conservative Union, a right-leaning group, each published ratings of lawmakers based on their votes for select bills during the 2015 session.

According to the American Conservative Union, “Delaware legislators with the strongest scores voted most consistently with the ideals articulated in the US Constitution: limited and transparent government, individual rights, personal responsibility and a healthy culture.”

The Americans for Democratic Action said its judgment indicates who most supported “progressive” ideals and served “as champions for social and economic justice issues.”

Each group singled out 10 bills of special interest to their respective causes. For the American Conservative Union that included legislation on taxes, gun restrictions and electronic cigarette limitations, while minimum wage, capital punishment and marijuana decriminalization were among the Americans for Democratic Action’s priorities.

Both scorecards judged lawmakers on how they voted on bills covering testing opt-out and granting driving privilege cards to people who entered the country illegally. The two groups supported opt-out but differed on driving privilege cards, with the American Conservative Union opposing. Unsurprisingly, the organizations took different stances on proposed tax increases as well.

Six legislators — three senators and three representatives — earned the Americans for Democratic Action’s highest grade (“hero”) and the American Conservative Union’s lowest designation (member of the “radical left”).

Fitting the state’s ideological divide, all are from northern New Castle. Wilmington Sens. Margaret Rose Henry and Harris McDowell, New Castle Sen. David McBride, Wilmington Reps. Charles Potter and Stephanie Bolden and Newark Rep. Paul Baumbach drew the most liberal rating from the two groups.

“I feel I need to represent the district that elected me to office and the issues that my district is concerned about are issues that are probably thought about being more liberal,” said Sen. Henry, who described “equal rights for everybody” as one of her main priorities.

The American Conservative Union recognized Rep. Rich Collins, R-Millsboro, for taking stances in line with the its views nine times, and Rep. Lyndon Yearick, R-Camden, and Sen. Colin Bonini, R-Dover, for doing so eight times apiece.

“I’m flattered to have been recognized,” Rep. Collins said in a news release. “I do not cast votes with anything in mind other than the best interests of the people I represent and what I believe to be right. So it was a pleasant surprise to be honored in this way by the ACU.”

The American Conservative Union also includes a lifetime average. Sen. Bonini, in office since 1994, agrees with the group 94 percent of the time, according to its metrics. Second is Sen. Brian Pettyjohn, R-Georgetown, who has earned an 84 percent rating since his election in 2012. Sen. Henry, who was elected in 1994, has a 0 percent rating.

Reps. Collins and Yearick, who were elected in 2014, have the highest lifetime ratings. Rep. John Viola, D-Newark, in office for 17 years, is the lowest representative, at 0 percent.

The average House Republican voted with the group 59 percent of the time in 2015, while the typical House Democrat did so on 17 percent of bills. In the Senate, the Republican mean was 53 percent, while the Democratic caucus scored 13 percent.

In total, the Americans for Democratic Action gave 14 officials its highest grade. All are Democrats, and Rep. Sean Lynn, of Dover, is the only one from below the Chesapeake and Delaware Canal. Thirteen lawmakers voted with the American Conservative Union 10 percent of the time or less on the 10 key bills it highlighted.

Fifteen members of the General Assembly received a zero from the Americans for Democratic Action, including Sen. Bruce Ennis, D-Smyrna, one of two lawmakers from New Castle and the only Democrat in the category.

History

Despite Delaware’s national reputation as a solid blue state, it has a diverse political history.

“Delaware in the presidential used to be a reliable bellwether since 1952 all the way up until the 2000 election,” Dr. Sam Hoff, a political science professor at Delaware State University.

For nearly half a century, voters selected the candidate who ended up winning, a streak broken when Delawareans went for Al Gore over George Bush in 2000.

While the state may have an undeniable Democratic lean, it is “not exactly Maryland or D.C. in context of our strong leftist ideology,” Dr. Hoff said.

As evidence, he cited the state’s efforts to abolish the death penalty. A much-anticipated vote in the House failed last month, despite Gov. Jack Markell’s public support of repeal.

All of the state’s federal lawmakers are Democrats. From 1992 to 2000, two of the three members of Delaware’s congressional delegation were Republicans. In 2000, outgoing Gov. Tom Carper defeated Republican Sen. Bill Roth in a heavyweight fight. For another decade, Sens. Carper and Joe Biden, a fellow Democrat who has since moved on to a much bigger stage, served in Congress along with Republican Rep. Mike Castle.

Famously moderate, Rep. Castle figured to coast to victory in the 2010 Senate election against New Castle County Executive Chris Coons, a Democrat. However, he was upset in the primary by tea party favorite Christine O’Donnell, who then lost in the general election.

Former Lt. Gov. John Carney, a Democrat, won the race for state’s lone House seat that year, giving Delaware three Democrats in Congress.

Locally, Democrats have controlled the Senate since 1973, but the two parties traded control of the House for about a decade after the Republicans captured the chamber in the 1984 elections. The state also elected two two-term Republican governors with Pete du Pont serving from 1977 to 1985 and Mike Castle from 1985 to 1992.

Since then, voters have chosen three two-term Democrats to lead the way. Only Washington and Oregon have longer uninterrupted active streaks of Democratic leadership.

Demographics, Dr. Hoff said, help explain the First State’s shift to the left. According to the U.S. Census Bureau, the state’s population was about 19.2 percent black and 4.8 percent Hispanic in 2000. In 2014, it was about 22.2 percent black and 8.9 percent Hispanic.

Those changes may seem small, but they represent an increase of more than 100,000 minorities, who traditionally vote Democratic.

The gap in registration totals has skyrocketed, data from the Delaware Elections Department shows. From 2000 to 2015, Democrats gained about 93,000 voters. Republicans? Just 10,000.

Today, there are about 309,000 Democrats, 183,000 Republicans and 163,000 independents. Even if many of those Democrats and independents are moderate voters who could be persuaded to vote for a Republican, the numbers seriously disadvantage the GOP.

Sen. Greg Lavelle, R-Sharpley, believes the Iraq War played a part in that disparity. Millennials, who hold more liberal views than other age groups, may have registered their disapproval with President George W. Bush and what they saw as a pointless war by registering as Democrats.

A general shift in attitudes on issues such as marijuana and gay marriage also has helped Democrats, both locally and nationally.

State Republican Chairman Charlie Copeland said Democratic leadership has done a good job of getting black voters onboard and giving party candidates a “20-point head start against your Republican opponent.”

While Republicans are cautiously optimistic about the November contest, 2016 is a presidential election, which typically benefits Democrats, as more voters come out than in mid-term elections. The presidential boost can aid down-ballot Democratic candidates.

In 2008, the Barack Obama wave helped sweep the Democrats into control of the House, just six years after they were outnumbered 29 to 12.

In some respects, the chambers, like American politics as a whole, have grown more polarized. Some of the Democrats who tended right and Republicans who slanted left, such as Democratic Sens. Thurman Adams and Robert Venables and Republican Rep. Bill Oberle, have died, been defeated or retired.

The majority caucuses each include relatively progressive and moderate wings, particularly in the House.

Though Delaware seems almost certain to remain a Democratic state after this election cycle with Rep. Carney running for the open governorship and several officials well-entrenched in their seats, it has often been said that politics is cyclical.

An economic downturn could see voters move away from the Democratic Party, perhaps voting a Republican into Woodburn for the first time in a quarter-century. Like most Delaware Republicans, Sen. Lavelle believes the state’s economic recovery has lagged, and he hopes Millennials start to vote with their wallets.

A major scandal, particularly involving a Democratic governor, could also help the minority party, Dr. Hoff noted. Indeed, Treasurer Ken Simpler’s 2014 win can partly be traced to frustrations with incumbent Chip Flowers, a Democrat who clashed with both the executive and legislative branches and had his deputy treasurer charge the state thousands of dollars for personal expenses.

Mr. Simpler’s win in 2014 was the first statewide win by a non-incumbent Republican since 1994. The party will look to continue that momentum this year, although numbers — and thus, money — are not on its side.

Still, nothing is set in stone.

“If we know how things turn out we wouldn’t have elections,” Sen. Lavelle said.