By FRED BARNES

Democrats across the country are celebrating the re-election of President Obama and the pickup of two seats in the Senate and eight in the House. But in two formerly Democratic states, Republicans have much to be joyful about.

The GOP victory in North Carolina included the governorship, veto-proof majorities in the state Senate and House, control of 54 of the state’s 100 counties, three new U.S. House seats, and a pivotal seat on the state Supreme Court. All this lifted Mitt Romney to a narrow victory in a state that Mr. Obama won in 2008.

It is premature to declare North Carolina a reliably red state, but Republicans are “positioned to be the dominant party in North Carolina for at least a decade if not beyond,” says GOP consultant Marc Rotterman.

The same is true in Arkansas, the second-best state for Republicans in last month’s election. Both states offer Republicans an opportunity to unseat Democratic senators in 2014. In Arkansas, the GOP trend has moved so quickly that Sen. Mark Pryor, who had no Republican opponent in 2008, is now considered highly vulnerable. In North Carolina, Sen. Kay Hagen, when matched against an unspecified Republican challenger, led just 45%-41% in a Public Policy Polling survey last month. The last Democratic senator to win re-election in North Carolina was Sam Ervin in 1968.

Republicans in the Tar Heel State were unified, with all elements of the party, including social conservatives, engaged with the various campaigns. The GOP ticket was ideologically balanced, with moderate gubernatorial candidate Pat McCrory at the top. The party, Republican campaigns, and GOP-oriented groups joined in a massive turnout operation. Republicans exploited every opening that Democrats gave them—and there were plenty.

Associated PressPat McCrory

The administration of incumbent Democratic Gov. Beverly Perdue—though not Ms. Perdue personally—was marked by scandals. The John Locke Foundation, a conservative think tank, uncovered numerous instances of misconduct and reported them in its publication, Carolina Journal. Gov. Perdue’s job approval sank to 25%, making her the second-most unpopular governor in the country (behind Pat Quinn in Illinois).

That wasn’t all. In 2007, Democratic House Speaker Jim Black was convicted of taking a $25,000 bribe. In 2009, the law license of Gov. Perdue’s predecessor, Mike Easley, was suspended after his conviction on a campaign reporting violation, a felony. And this year, the state Democratic Party was hit by a sexual-harassment scandal.

“There was a culture of corruption because Democrats were in power for so long,” says John Hood, president of the Locke Foundation. “And there were crooks.”

The timing of these Democratic scandals was propitious for Republicans, who in 2010 captured the state legislature for the first time and earned the opportunity to reapportion legislative districts, also for the first time in the state’s history. Republicans seized the moment, undoing more than a century of Democratic gerrymandering.

They forced the retirement of two Democrats in the U.S. House, Heath Shuler and Brad Miller, and helped cause the electoral defeat of a third, Larry Kissell. To improve GOP prospects, Republican incumbent Congressman Patrick McHenry agreed to have liberal Asheville shifted into his district. Having won his seat with 71% of votes in 2010, he still won re-election comfortably this year, 57%-43%.

The linchpin of the Republican sweep was Mr. McCrory, the gubernatorial aspirant. Mayor of Charlotte from 1995-2009, he lost a close contest for governor in 2008 but ran a nearly flawless race this time, significantly outspending his opponent and imposing his issues as the focus of the campaign. His message was simple: “We must fix North Carolina’s broken economy and broken state government, and with new leadership we can bring about a Carolina comeback.”

Given his reputation as a moderate, Mr. McCrory made a point of broadening his support by appealing to conservatives. He backed a voter ID law. More important, he endorsed an amendment on the ballot in the May primary that established traditional marriage as “the only domestic legal union” valid in the state. “You don’t desert things like that,” says Jack Hawke, Mr. McCrory’s chief strategist. The amendment passed, 61%-39%.

The marriage issue energized evangelicals and social conservatives. “It kept them involved for the entire campaign,” says Mr. Rotterman, the consultant. Mr. McCrory also overwhelmingly won independents, belying the notion that wooing social conservatives alienates others, independents especially.

Mr. Romney was a major beneficiary of the GOP success. Campaign buzz around a partial pullout of Obama operatives proved to be false, and in fact Mr. Obama expanded his North Carolina operation in the closing weeks, even dispatching Joe Biden and Bill Clinton to appear at rallies. The president likely would have won the state absent the boost that down-ticket Republicans gave Mr. Romney.

Now Mr. McCrory, the first Republican governor in two decades, must revive the state’s economy, which has the nation’s fifth-worst unemployment rate, at 9.3%. He wants to use tax reform to cut business and individual income taxes (top rate 7.75%) and tap the state’s oil and natural-gas resources, all while overhauling state government. If he succeeds, he’ll build a durable Republican majority.

Tom Jensen, the director of Raleigh-based Public Policy Polling, says the Democratic Party in North Carolina is “broken” and leaderless. But former four-term Gov. Jim Hunt remains active and the party’s longtime alliance with big business is weakened but not dead.

In Arkansas, by contrast, the Democratic Party barely exists. With the Clintons gone, it has no center, and Republicans have swept to power in only two years. In 2010, Republican John Boozman ousted Democratic Sen. Blanche Lincoln, 58%-37%. This year, Republicans took the state legislature and Tom Cotton, the star Republican freshman of the 2012 class, won the state’s last Democratic-held seat in Congress. Mr. Romney won Arkansas by 25 points. Democratic Gov. Mike Beebe is term-limited and leaves office in 2014.

The lesson from the two states where Republicans did the best in 2012 are hardly new ones. Party unity matters. There is no substitute for good candidates. Broad-gauge, inclusive conservative campaigns tend to prosper. Simple as that.

Mr. Barnes is executive editor of the Weekly Standard and a Fox News commentator.