Former Secretary of State Hillary Clinton and Massachusetts Democratic Sen. Elizabeth Warren are reportedly developing a close political friendship that might prove pivotal to deciding the Democratic presidential nomination.

Both have kept in touch since Warren announced her decision to seek the Democratic nomination last February, NBC News reported Saturday.

One source close to NBC told the media outlet that the two had conversed at least once since Warren’s announcement, while another could recall a recent, substantive conversation that was “front of mind.” (RELATED: CNN Panel Gets Heated When Trump Comes Up In Debate On Warren-Clinton Comparison)