The opposition research group American Bridge made its mark in the 2012 election cycle with a video clip of a Missouri Senate candidate, Todd Akin, saying that “legitimate rape” rarely leads to pregnancy.

Republicans running in other states, as well as the presidential nominee, Mitt Romney, found themselves answering questions about him.

In 2016, the group is taking every opportunity to do the same thing with Donald J. Trump. It is maintaining an archive of digital video footage, with 6,500 clips of Mr. Trump speaking or being mentioned, going back to the 1980s, and 17,000 hours of footage over all. It has also compiled more than 5,000 pages of research on the presumptive Republican nominee and has 25 trackers monitoring him.

American Bridge is playing a more significant role in 2016 than it did in 2012, when the Obama campaign was leery of the group, which was founded by a close ally of Hillary Clinton’s. This cycle, Democrats have relied on it openly for research.