PM Takaichi's Liberal Democratic Party is likely to win between 274-328 seats in the Lower House, higher than the 233 seats needed for a majority, NHK says.
A bill that would make it harder to vote in federal elections is a Republican focus this week, with President Donald Trump calling for enacting the SAVE Act.
The depiction of the Obamas, posted from Trump's Truth Social account, was included in a video pushing a conspiracy theory about 2020 election voting machines.
It follows a contentious decision from Panama's top court to rule against a Hong Kong-backed firm's right to operate two key terminals on the waterway.