For the first two years of her tenure, some supporters of Philippine Vice President Leni Robredo wanted to see her stand up more forcefully against Philippine President Rodrigo Duterte. Now, it looks like they might finally be getting their way.

"It is becoming apparent that people will be more confident to speak up if there is another group that shares the same beliefs," she announced earlier this month. "And that’s the role I want to take, to unite those voices."

Elected to be Duterte's number two, despite being from the opposition Liberal Party, Robredo occupies a unique role in Philippine politics. As the most visible and high-profile member of the opposition, she appears to have the ideal profile for taking on President Duterte, who has drawn widespread criticism for a deadly drug war and his pugnacious public attitude.

But Robredo has spent her time as vice president walking a rhetorical tightrope, seeking to be critical of Duterte when necessary, but often avoiding taking him on directly.

This, however, seems to be changing. Sensing a political opening ahead of the 2019 midterm elections and following several high-profile scandals for Duterte — most notably, when he referred to God as "stupid" earlier this summer, a major faux pas in the deeply Catholic country — Robredo has sharpened her criticism and is beginning to embrace the role of de facto opposition leader.

"Leni has stepped up her rhetoric," Richard Heydarian, a Manila based-academic and author of a Duterte biography, told DW.

"There was kind of a calculation that the 'God' comments of Duterte were going to really alienate his base, and that this is a perfect opening for her to come in stronger."

A stronger tone

Back in early 2017, Robredo tried her hand at criticizing Duterte when she told the UN that the president's bloody drug war was leaving Filipinos feeling "hopeless and helpless." Government estimates say that about 3,000 people have been killed in the campaign since Duterte took office. However, independent observers such as Human Rights Watch, have said the true total is at least 12,000 or more.

"Some people have told us that when there is crime, they normally go to the police. Now, they don't know where to turn," Robredo said in a video message at the time. "Our people feel both hopeless and helpless, a state of mind that we must all take seriously."

The comments caused problems for Robredo back home, where a group of Duterte supporters filed a petition to impeach her and House Speaker Pantaleon Alvarez said she was guilty of "betraying the public trust."

Read more:Philippine's Rodrigo Duterte urges nations to abandon International Criminal Court 

Others suggested that, because she is the vice president, her criticism was essentially self-interested and that she was trying to take Duterte’s job out from under him.

"Her situation is damned if you do, damned if you don’t," said Heydarian. "The fact that she’s constitutionally in line of succession makes her always suspect in the eyes of the administration."

Robredo's aides say she has been holding her fire in an effort to make sure that her words still have power when she decides to speak out. Barry Gutierrez, Robredo's spokesman, referred to the ex-Senator Leila de Lima, currently serving a jail term for alleged ties to the drug trade, as a cautionary tale. De Lima began criticizing every move Duterte made as soon as he took office, Gutierrez said, which made people stop taking her arguments seriously.

"That’s what the vice president is trying to avoid," he told DW. "How credible will you sound if you just continue to appear to be against everything this guy does?"

Midterms on the horizon

However, with midterms coming up next year the stakes are higher. And with a fairly disorganized opposition, Robredo could be a unifying force.

"In the last few weeks, she's been stronger in her statements than at any other time before," Gutierrez said. "I think that's also due in part to an increasing sense of dissatisfaction among the electorate," he added.

Last month, for example, Robredo said China's emboldened position in the South China Sea is the "most serious external threat" to the Philippines since the Second World War, which was a jab at Duterte for his increasingly cozy relationship with Beijing.

Read more: 'Philippines, province of China' banners spark fury in Manila

Robredo was also critical of the push for federalist constitutional reform in the Philippines, saying the effort in its current form is being used "to put forward private interests and not the interest of the public."

The opposition may see Robredo as its best hope for a public face, but Duterte spokesman Harry Roque dismissed her as "virtually useless" in her current position. Since Robredo gave up her cabinet posting in December 2016 as head of the Housing and Urban Development Coordinating Council, Roque said she has no real power.

"The problem with her is she doesn't really know what role she wants," he told DW. "[Duterte] was willing to work with her and she blew it."