Complex sentence: Political parties may run up to as many candidates as there are available seats in each electoral district; major parties will typically run several candidates (though generally not more than they might expect to be successfully elected) while smaller parties might run only single candidates.
Split into simpler sentences: Political parties may run up to as many candidates as there are available seats in each electoral district. Major parties will typically run several candidates (though generally not more than they might expect to be successfully elected) while smaller parties might run only single candidates.