From 2003 to 2009, he served as the state representative from District 38, which includes most of Lake Oswego and portions of southwestern Portland.

His paternal grandfather, Hector Macpherson, Sr., was elected in 1926, 1928, and 1938 as a progressive Republican member the Oregon Legislative Assembly.

[4][5] In 2002, Macpherson was elected to the Oregon House of Representatives, defeating Republican Jim Zupancic.

[6] In 2006, Macpherson was one of only three Democrats in the Oregon legislature who urged the PUC to oppose refunding Portland General Electric (PGE) customers who had been illegally overcharged by the utility.

He was a candidate for Oregon Attorney General in 2008, running to succeed incumbent Hardy Myers, but lost in the Democratic primary to John Kroger.