Sinn Féin’s President Elect, Mary Lou McDonald, has described Michelle O’Neill as a "formidable woman".
The party’s Stormont leader is understood to be the only person in the race to be the party’s next deputy leader.
Nominations close tomorrow before a special Ard Fheis next month.
Ms Lou McDonald, who will replace Gerry Adams as party leader, has told Q Radio Ms O’Neill is "a very strong candidate".
She said: "She may prove to be the only contender, she’s hugely popular right across the party, north and south.
"So, I’m not surprised that she’s receiving strong nominations, but you can never rule out that another candidate could step forward."