Since 1898, Puerto Rico has had limited representation in the Congress in the form of a Resident Commissioner, a nonvoting delegate. The 110th Congress returned the Commissioner's power to vote in the Committee of the Whole, but not on matters where the vote would represent a decisive participation. Puerto Rico has elections on the United States presidential primary or caucus of the Democratic Party and the Republican Party to select delegates to the respective parties' national conventions although presidential electors are not granted on the Electoral College. As American citizens, Puerto Ricans can vote in U.S. presidential elections, provided they reside in one of the 50 states or the District of Columbia and not in Puerto Rico itself.
Which Congress gave the democrats the power to vote?