I'm thinking 35k+ in attendance tonight.
Could very well be, given that they've been winning and it's not going to be quite as goshawful-hot as at the weekend.
Best Nats home attendance on a Tuesday, either ballpark: 41,517 at Nats Park vs Red Sox, 23rd June 2009
Best Nats Park Tuesday attendance to date in 2012: 27,835 vs Rays, 19th June
Best Nats home attendance on 3rd July, either ballpark: 39,214 vs Mets at Nats Park, 2010 (a Saturday with a Strasburg start)