History. 7 of 7: every president facing a new Congress where the other party had just won both chambers vetoed one of its bills within 178 days; the latest was Clinton in 1995, on day 154.
Hunch. Republicans will still hold at least 44 Senate seats, enough to block most Democratic bills under the 60-vote rule, the Guardian reported on 8 November.
The 1 July market resolves on the same pages: YES if by 30 June 2027, Washington time, Trump vetoes a bill or joint resolution of the new Congress, and a veto of a bill of the old Congress does not count. If there is no such veto it resolves NO, and the Guardian, BBC News and NPR are the backups.
We looked for cases where the party opposed to the president had just won both chambers of the US Congress, and counted the days from the first sitting of that new Congress to the president's first veto of one of its bills. Since 1919 this has happened seven times. Each of those presidents used a veto in the first year. (US House of Representatives; US House of Representatives; American Presidency Project)