I suspect the Democrats have a strong chance of holding on to the governorship. Why? Well, half of the Kansas Democratic Party consists of Republicans cinverted by Sebelius (only a slight exaggeration), so Parkinson definitely has the support for the primary. Sebelius's endorsement alone would probably be enough for a landslide. (AG Paul Morrison is another likely candidate for governor if Parkinson turns it down.)
Secondly, the Kansas GOP is severely divided between radical conservative and moderate branches--the moderate branch having increasingly defected to the Democrats since the radicals took over the party around 2002. The Republicans are likely to nominate another kook for governor and be destroyed.
Although, given the title of this thread, it's probably supposed to be about the Senate despite the section of the forum. Brownback is retiring; the Republican candidate for Senate is very likely to be Rep. Jerry Moran. Sebelius could defeat Moran, but certainly no one else in Kansas could.
I would not bet on the Democrat's chances if
former AG Paul Morrison was their candidate
