before unexpectedly endorsing a Liberal

[Flogger]

Hello

I cannot understand the red part. Actually, I have both problems with its grammar and meaning. Would you help me?

In a late August campaign stop in Winnipeg, indigenous leaders appeared with Singh at a press conference before unexpectedly endorsing a Liberal in a Manitoba parliamentary constituency.

 

[jutfrank]

The indigenous leaders unexpectedly endorsed a Liberal. They did this after they appeared at a press conference with Singh.

 

[probus]

For a little further clarification, Singh is the leader of a political party that opposes the Liberals. The author is implying that the indigenous people were likely to support his party -- that was why they held a joint press conference with him.