2 turntables and one phono stage - Can I???

Spliiting that will degrade the sound. Keep in mind the siganl coming from the cartridge is a weak and EMI/RFI vunerable signal. If you must do this for budget reasons till you can aquire a second phono stage. You would be best served by looking at AudioQuest splitter blocks, these can be found at most audio web sites. Audioadvisor.com for example.

No, you cannot use a splitter at the input to a phono stage, not even the AudioQuest splitter. The reason is that cart has very low internal impedance. When you put two carts together in a splitter, they are effectively shorting each other out.

Your best option other than replacing the phone stage is to get a high quality mechanical A/B switch.

As Sidssp inferred, you COULD use a splitter, if you also used a switch, so that the phono circuit was only "seeing" one of the two cartridges at any one time, or to put the same concept in another way, so that the cartridge you are listening to will not "see" the other cartridge in parallel with the phono input impedance. This probably would require an outboard box containing a switch plus two pairs of phono inputs. If you decide to do that, just hard wire the from the internal leads to the one phono input on your preamp (i.e., I would advise you to avoid using yet another pair of ICs with another set of RCAs to do this).