McCollum has worked as a high school social sciences teacher and as a sales manager.

[3] After 4th district Representative Bruce Vento decided not to seek a 13th term due to illness in 2000 (he died before the election), McCollum won the DFL nomination to succeed him.

McCollum's main concern during the campaign wasn't her Republican opponent, State Senator Linda Runbeck, but Independence Party candidate Tom Foley.

According to the McCourt School of Public Policy at Georgetown University, McCollum held a Bipartisan Index Score of -0.1 in the 116th United States Congress for 2019, which placed her 219th out of 435 members.

[20] She indicated on the 2002 National Political Awareness Test that she believed abortions should always be legally available, but only within the first trimester of pregnancy.

She has backed organizations such as the Alliance for Retired Americans and the National Committee to Preserve Social Security and Medicare, which share the mission to ensure social and economic justice and full civil rights for all citizens so that they may enjoy lives of dignity, personal and family fulfillment and security.

"[26] McCollum advocates shifting America's energy consumption to cleaner, non-carbon-based sources.

[21] In July 2019, McCollum voted against a House resolution introduced by Representative Brad Schneider of Illinois opposing the Global Boycott, Divestment, and Sanctions Movement targeting Israel.

The bill requires the State Department to file an annual report to Congress detailing the extent to which U.S. aid from the previous fiscal year was used to bankroll any of the aforementioned activities.

[34] On July 19, 2024, McCollum called for Joe Biden to withdraw from the 2024 United States presidential election.