Moldova and Romania speak the same language and reunification has been a possibility since independence. This Jan 2022 article quotes a poll finding 44% support in Moldova for union with Romania.

That was before Russia invaded Ukraine. Romania is in both NATO and the EU, so by joining Romania, Moldova could essentially shortcut the membership requirements for both organisations at the cost of giving up sovereignty. This bargain looks a lot more attractive now that the perceived risk of Russian invasion is higher. I note Metaculus already has a question on whether Russia will recognise Moldova's breakaway region Transnistria this year.