During last year’s presidential election, a team of South Korean intelligence agents allegedly flooded the Internet with several thousand political comments, including some describing left-leaning candidates as North Korea sympathizers.

Then, while that scandal continued to play out, another drama unfolded. The spy agency last month declassified a 2007 transcript that showed then-President Roh Moo-hyun, a liberal, pressing to create a peace zone along a maritime border disputed with the North.

Conservative lawmakers say the transcript proves Roh preferred to cooperate with Pyongyang than protect security. Liberal lawmakers say the spy agency, instead, was manufacturing one controversy to distract from the other.

The two events are convoluted, but both have dominated headlines for weeks in the South. They also have a common thread: South Korea’s National Intelligence Service (NIS), which some analysts here say has turned into a political provocateur, using its power to champion conservative causes and widen a partisan divide.

Because of its Stalinist neighbor, the South has long defined itself along Cold War lines, with political ideology here linked in part to one’s sentiment about the North. But in the 2012 election, that had appeared to be changing. On the campaign trail, conservative Park Geun-hye and liberal Moon Jae-in shared similar visions for social spending and tentative engagement with the North. When Park won by three percentage points, she vowed to unify the nation.

In the six months since her victory, that has not happened, and Park’s opponents criticize her for staying quiet about the spy agency’s actions rather than condemning them. Only last month did she first discuss the alleged election meddling — the first parts of which came to light in December — saying she had was neither connected to nor a beneficiary of the agency’s potential misdeeds.

“I don’t think this allegation puts her legitimacy in question,” said Kang Won-Taek, a right-leaning professor of political science at Seoul National University. “How many people’s opinions could have been affected by some Internet postings? But it’s true that it’s not a pretty scene for Park” to deal with.

Her approval rating remains high — above 60 percent, according to most polls. But opposition lawmakers have seized on the election-tampering charges to raise questions about Park’s victory, and small groups of protesters have gathered in recent days in cities across South Korea to demand an investigation and a greater response from Park.

The NIS, South Korea’s version of the CIA, is supposed to remain politically neutral. But prosecutors say its former leader, Won Sei-hoon, indicted last month on charges of election meddling, believed that “leftist followers of North Korea” were trying to regain power in the South. He ordered his agents to post comments not only criticizing Park’s opponents but also lauding Park, prosecutors say. Won resigned this year, having served under the previous president, Lee Myung-bak. If found guilty, Won will face up to five years in jail.

“It is grave — a big deal. It’s all about dividing the country into two parts — the patriots and those who sympathize with North Korea,” said Pyo Chang-won, who hosts a current-affairs Internet show and has spoken at protests. “The NIS is supposed to be politically neutral, but it has used its intelligence force to attack half the nation.”

Left-leaning lawmakers say the problems at the NIS have continued under Won’s successor, Nam Jae-joon, who they say unilaterally released a document that should not have been made public for decades. At a closed-door meeting of the National Assembly’s intelligence committee late last month, Nam was grilled about the release, according to South Korean media, and asked whether he had any intention to resign. (He said he did not.)

South Korea’s intelligence agency has gone by several names since the Korean War 60 years ago, but it has a dubious history. Former authoritarian leader Park Chung-hee, who seized power in a 1961 military coup, used the agency as a tool to crack down on student protests. In 1979, Park was assassinated by his own spy chief.

After South Korea’s democratization in the late-1980s, the agency officially became apolitical. But opponents say the agency is now helping Park Geun-hye in much the way it helped Park Chung-hee, her father. Monday, the Hankyoreh, South Korea’s major liberal newspaper, printed a cartoon showing the president, in a military outfit, surrounded by cronies holding computer keyboards and mouses. The image was modeled after a photo of Park Chung-hee, flanked by top military officials, after his coup.

Analysts say the alleged election tampering is far more serious than the debate about the 2007 transcript. But that controversy, too, has provided weeks of fodder for South Koreans.

The transcript showed the conversation between Roh and then-North Korean supreme leader Kim Jong Il during a summit meeting in Pyongyang. Interest in the specifics of what Roh told Kim dated to last year, when some conservative lawmakers suggested that Roh had offered to surrender parts of South Korean maritime territory in an undisciplined effort to make peace with the North. The charge was potent, because the liberal running for president last year, Moon, had once served as Roh’s chief of staff.

According to the transcript, while discussing the maritime border, Roh said that it “should change.” But he also said, presciently, that the issue was touchy. “The problem is that whenever the [maritime border] is mentioned, everyone rises and makes noise like a swarm of bees,” Roh said.

In the closest she has come to taking a side on the issue, Park, one day after the transcript’s release, told her cabinet that the South should never forget the “blood and deaths” that occurred in defense of that border.

Yoonjung Seo contributed to this report.