The allegation itself is news, but it's important to label it as such when reporting it. The next step is to investigate it.
If Trump says there are extraterrestrials living in Area 51 that's news regardless if you can verify it.
If I, random nobody, show up with an allegation against Trump, using unverifiable "evidence," then that allegation is not newsworthy.
And doubly-so if my whole job is to be a partisan hack trying to delver an October surprise.
The allegation itself is news, but it's important to label it as such when reporting it. The next step is to investigate it.
If Trump says there are extraterrestrials living in Area 51 that's news regardless if you can verify it.