Do you have to keep the idea of nullification under wraps? Revealing your intentions would definitely reveal bias...
Most certainly. I have observed many jury selections because I used to testify as an expert witness as part of my job.
Prosecutors
always fight to exclude any potential juror they think might harbor "nullification" tendencies.
Actually, the standard procedure I witnessed was that both the Prosecutor and Defense Attorneys would give each other five "ringers" (ringers being people they stereotyped as likely to vote for their side), then they would fight over the remaining two jurors.
Both sides
always excluded any person they thought would be a fair and impartial judge of the facts. As with so many things, court proceedings are the exact opposite of what they are advertised to be.