In the Senate race there two years ago, Warner led Gillespie two years ago by 9-10 points. He won by a point.
Also, Senate polls in 2014 overstated Dem support by an average of 4 points in the last three weeks.
The $2 million buy is a head-scratcher to me as well, but perhaps they know something we don't.
That likely is what Trump is thinking, he's going for a hail mary pass.
I doubt it will work out for him. In 2014, Democrats didn't turn out, because most people don't care that much about midterms and everyone just assumed Warner was a shoe in. I doubt the same thing will happen in a presidential election, let alone one as high profile as this one has been.
Also, Gillespie was a decent fit for the state (Virginia seems to have a soft spot for insiders). Trump is the absolute worst fit imaginable.