Highly unlikely - Republicans are up by over 20 points with early voting.
Republicans are not necessarily voting for Brownback. That's why this is a race.
The last numbers I saw had Republicans at 53% and Democrats at around 30%, with the rest Independents. If Brownback is losing that sample by 19% he is on his way to a landslide defeat.
Party registration and party ID can wildly differ. The Monmouth poll in Kansas with Davis up 5 had this:
Party registration:
60% R
25% D
15% I
Party ID:
42% R
24% D
34% I
Registered Republicans who self identify as independents are exactly the type of people who would break overwhelmingly for Davis. If they weren't doing so, this would be a Brownback landslide.