What restrictions does the constitution place on the states in setting suffrage qualifications?

Five restrictions have been placed on the states, at current. First, those citizens who are able to vote for the most numerous branch of state government are allowed to vote for representatives to the House of Representatives. Second, the 15th Amendment outlawed voting discrimination on the basis of race. Third, the 19th Amendment gave women the right to vote. Fourth, there is an abolition on poll taxes as part of the 24th amendment, extended to the states in 1966. Finally, the 26th Amendment lowered the national voting age to 18 years for state elections.