Colombian President Juan Manuel Santos has a problem: his predecessor and former boss, Álvaro Uribe.

During the 2010 presidential campaign, Uribe backed Santos as the most capable steward of his hard-line, U.S.-supported policies that brought a once-chaotic country under control. Now Uribe calls his former defense minister “a traitor” and “a scoundrel,” warning of the doomsday scenario that awaits if peace negotiations with Marxist guerrillas are fruitful.

Uribe has even formed his own political party, the Uribe Democratic Center, and says he’ll run for senate to block his former underling’s initiatives.

The relentless attacks from Uribe, who was the closest U.S. ally in Latin America during his eight-year rule, is raising eyebrows among policymakers in the Obama administration and in the U.S. Congress. Both Uribe and Santos were central to the war on drugs in the Andes, a battle largely funded with billions of dollars in U.S. military aid, and analysts say the effort to undermine the Santos presidency is seen as unseemly.

“We are not accustomed to ex-presidents playing such an explicit role, opining on the decisions of a sitting president,” said Carl Meacham, who for 10 years oversaw Latin American policy for Republicans on the Senate foreign relations committee. “For us, it’s sort of shocking to see the extent of President Uribe’s involvement.”

Sen. Patrick J. Leahy, (D-Vt.), chairman of the appropriations subcommittee that funds U.S. aid to Colombia, said it was regrettable that “some Colombian politicians” were seeking “to sabotage a process that may be Colombia’s best hope to finally put an end to decades of violence.”

The Santos bashing seems to have gathered strength and attention in recent weeks as Colombians have become less hopeful about peace talks with the Revolutionary Armed Forces of Colombia, or FARC, a rebel group that polls here show most people loathe. Santos’s approval rating has plummeted to 21 percent from 48 percent in June, according to a Gallup poll carried out last month.

‘Impunity to the terrorists’

Uribe’s onslaught comes at a particularly challenging moment. Santos, 62, needs the negotiations to advance to bolster popular support for a successful reelection campaign next year. But the talks have bogged down in part because of FARC delaying tactics, giving Uribe more ammunition.

“It’s a huge problem, especially because he’s one of the most popular politicians in the country,” Adam Isacson, a senior analyst at the Washington Office on Latin America, said of Uribe.

Uribe, 61, whose father was killed by FARC guerrillas, contends that Santos betrayed his administration’s legacy by repairing relations with Venezuela’s leftist government, which assisted the rebels, and then embarking on negotiations with the group’s commanders. He does not mention that when Santos was his defense minister, the Colombian security services delivered their most decisive blows against FARC.

Uribe recently tweeted to his 2.3 million followers that Santos has “converted terrorists who were in the process of being defeated and isolated into political actors.”

The Colombian people “have a right to candidates that do not betray us [with] one position during elections and another while in power,” he tweeted in another missive, this one in English.

In a recent interview with Bogota’s Blu Radio, Uribe went so far as to say: “Santos lies and is giving impunity to the terrorists.”

Criticizing the criticism

Santos defends his approach toward FARC, saying the group opted for peace talks to end a conflict that has cost 220,000 lives precisely because of the successful military strikes he had ordered.

“It would have been easy to move forward on the path that we were on, and to leave the conflict unresolved,” Santos said in a speech at the United Nations last month. “Waging war, and I know how to wage war, is much easier than seeking peace.”

But in tweet after tweet, Uribe has highlighted what he contends are breakdowns in security. He has acknowledged relying on details provided to him by loyal army officers.

One moment, he writes about a kidnapped cattleman, or a FARC attack on a town. A few months ago, he published photographs of two dead policemen killed by FARC, sparking an outcry among pundits who said he had gone too far.

For Uribe’s critics, it’s just too much.

“He is a profound narcissist, seeing himself as Colombia’s savior,” said Ivan Cepeda, a leftist congressman who has publicly tangled with Uribe.

Hector Abad, a novelist and columnist, said Uribe seems to relish disseminating any bad news that will embarrass Santos.

“I don’t think it’s so good that an ex-president, one with so much power and the capacity to influence Colombians, dedicate most of his time to being the one to reveal all the security problems and bad news,” Abad said.

Uribe’s spokesman did not return calls or e-mails seeking comment. But his supporters say he is simply trying to get Colombia back on the right track.

“We have decided to create a party so that these ideas can persevere,” said Uribe’s former vice president, Francisco Santos, who also happens to be the current president’s cousin.

Oscar Ivan Zuluaga, finance minister in the Uribe years, said Uribe’s drive to run for Senate “restores the trust, the hopes of millions of Colombians who want to restore security.”

Not everything is going his way. Prosecutors and investigating magistrates have been probing Uribe, his brother and associates of the former president for colluding with vigilante-like paramilitary groups.

Uribe’s new party has also been riven by rivalries, analysts note, and some of his political allies have been handily defeated in elections.

“I don’t think Uribe is a serious threat,” said Aldo Civico, a conflict resolution expert at Rutgers University who specializes in the Colombian conflict and has closely followed Uribe’s career. “And his noise is overblown by the Colombian media.”