How did the presidency change during the progressive era?

In general, the presidency as an office came to be much
more important during the Progressive Era than it had been
before.

In the late 1800s, the Presidency was very weak. 
Presidents did not exert themselves very much to try to affect policy.  Congress pretty
much ran the country.

Starting with Theodore Roosevelt,
this changed.  TR was the one who described the office as a "bully pulpit."  "Bully"
meant "really good."  He believed the office gave him the chance to really push the
people and Congress towards various ideas and
policies.

Because of this, and because the Progressives
wanted government to enact a lot of reforms, the Presidency got much stronger during
this time.