The real problem with being a true check is partisanship on the court. By now, it seems to be essentially accepted that there are "liberal judges" and "conservative judges", and that they will rule accordingly. I cringe every time I hear that, because SCOTUS, like any other court, is supposed to rule on what the law is, not on what it should be; and one's political affiliation should not affect the former. In practice, of course, it does matter these days, and it is a really bad thing, especially in an institution that is 1) so small, and 2) not providing any mechanism to hold them responsible.
And there is no evidence that electoral fraud is likely to decide the election. In fact it's looking like efforts to prevent it e.g. in Indiana are far more likely to influence the election.
He is down by on average 7 points nationally for a reason.
http://fivethirtyeight.com/features/for-many-gop-women-party...
Other types of fraud (ballot stuffing, voting multiple times, voting when you're not allowed to etc.) are exceedingly rare, and it would have to happen at a massive scale for it to make an actual impact.
That's just not going to happen, especially with it being a felony.