The answer is conjectured to be "yes." Further, assuming GRH and GSH [Rubinstein and Sarnak, Chebyshev's Bias, Exp. Math 1994](http://projecteuclid.org/euclid.em/1048515870) even could show results on the logarithmic densities of the resepactive sets (which in particular is non-zero). I do not know about general explicit upper bounds.

Without GRH a lot less is known. The problem you mention sometimes goes by Shanks--Rényi race problem. A very good exposition of this circle of ideas is [Prime Number Races by Granville and Martin](http://arxiv.org/abs/math/0408319); see page 22 and subsequent ones for the discussion of Rubinstein and Sarnak's results.