It wouldn’t invalidate the election. There are Constitutional mechanisms in place to deal with unqualified Presidential candidates. If it turns out that O isn’t qualified then either the EC selects the next President or House selects the next President (before the Inauguration) or (after Inauguration) O is impeached and convicted and Biden becomes President. If Biden is implicated and gets impeached and convicted then Pelosi becomes President, then Byrd, then the Secretary of State, and so on down the chain of succession. Biden is going to be the next VP, barring conviction for any involvement in a coverup, as the Electors cast their votes for POTUS and VPOTUS seperately and distinctly. In theory we could end up with McCain/Biden. But I personally have a serious problem with any appointments made by O if he turns out to be ineligible for the office. In any case, there will not be a new election. We already have a President-elect, we just don’t know who it is yet.
No, I believe his electors would be booted.