A special Senate committee starts its work Tuesday of digging into the circumstances surrounding the unsettled race to represent District 25 in the state Senate. The district encompasses some of Portland’s northern suburbs.

Depending on what the committee finds, the partisan composition of the state Senate could change by one seat. That shift would follow a significant change in the partisan makeup of the Legislature following November’s elections.

As it stands now, the Democratically controlled House has 79 Democrats, 68 Republicans and four unenrolled members. The Senate has 21 Republicans and 14 Democrats.

A century ago — during the 1915-16 legislative session — Democrats held a similar number of seats: 78 in the House and 14 in the Senate. There have also been times with no Democrats at all in the Senate, such as the 1921-22 session and 1929-30.

A scroll through the partisan makeup of Maine’s Legislature over the past century-plus shows the highs and lows for both parties. In cases when the makeup changed between elections, this count — made available by the Maine Legislature — uses the partisan makeup at the end of the legislative session.

Use the slider arrow on the graphic above to see how partisan makeup in the House and Senate changed over time.