Elizabeth Warren has quietly turned to Hillary Clinton as the Democratic presidential primary heats up.

The Massachusetts senator, one of more than a dozen Democrats running for president, has remained in contact with the 2016 Democratic nominee, NBC reported Saturday.

Both camps have kept quiet about what the two women have discussed and how many times they have spoken since their previously reported conversation around the time Warren, 70, launched her presidential bid.

A person close to Clinton, 71, said the contact between the two has been “substantial enough to merit attention.”

Warren has been polling in the top tier alongside former Vice President Joe Biden and Vermont Sen. Bernie Sanders, and Clinton’s support in the primary could help her win over voters who backed her in the 2016 primary against Sanders.

For now, Warren has done little to publicly connect herself to Clinton, who lost in a stunning defeat to President Trump and who was accused of being too centrist by Sanders supporters.

The 2020 candidate said earlier this year she would have accepted an offer from Clinton to become her 2016 running mate. Warren was interviewed for the slot, but Clinton ended up picking Virginia Sen. Tim Kaine instead.