If each state held a referendum on the death penalty...

[Tender Branson]

Which states would vote in favor of abolishing it?  Or, if they currently don't have the death penalty, which ones would vote against reinstating it?  Maps?

That would depend on the question wording of the referendums.

You can A) word it like "Do you support (re)-introduction/maintaining the death penalty for murder ?"

or

You can B) word it like "Do you support (re)-introduction/maintaining the death penalty for murder or do you instead support life in prison with/without the chance of parole ?"

...

Support for A) is usually at around 65% nationally (lower in strong DEM states, higher in GOP states).

Support for B) is usually around 45-45 in recent polls.

[Tender Branson]

If it's just the question "death penalty yes or no" without offering life with/without parole, then almost all states would vote for the death penalty right now.

There are hardly any recent state polls, but even in CA it's still at 55% support (remember that the close referendum vote in 2012 came only with big concessions in funding for victims and solving murder cases), NH supports it 2:1 and support in CO is 75% and 80% in OK ...