He served as an assistant majority leader of the House DFL caucus and as vice chair of the Energy and Climate Finance and Policy Committee from 2019 to 2020.

[9] As majority leader, Long has listed investments in affordable housing, child care, and climate change among his caucus's top priorities for the 2023 legislative session.

[16] Long has supported efforts to cut greenhouse gas emissions by decreasing reliance on coal plants and investing in solar panels, wind energy, and electric vehicles.

[40][41][42] Long has supported Walz's efforts to use his rule-making authority to adopt stricter car emission standards, and pushed for a state rebate program for electric vehicle purchases.

[47] Long founded a bipartisan Criminal Justice Reform Caucus in the Minnesota legislature, and pushed for automatic expungement of certain low-level crimes.

[55] Long led a criminal justice reform roundtable for 2020 Democratic Party presidential primary candidate Elizabeth Warren, and praised her policies on use-of-force standards and plan to end private prisons.

[61] Long authored legislation that would mandate PTSD training for public safety workers and change the process for police receiving state duty disability benefits.

[62] The bipartisan proposal would require treatment from medical professionals and officers to seek workers' compensation before being put on permanent disability under the pension system.

[63][64] Long has spoken out about the number of Minneapolis police officers seeking disability benefits, saying it could lead to some avoiding the normal disciplinary process.

[65] Long has called for legislation to open access to presidential primary ballots, allowing candidates to be listed if they file an affidavit and pay a fee.

[70][71] Long supports moving Minnesota from a part-time to a full-time legislature, saying the change would get rid of the need for last-minute special sessions, lessen the need for massive omnibus bills, and lead to more bipartisan discussion and agreement.

[72][74] Long sponsored legislation in 2023 to expand MinnesotaCare, the state's healthcare program for low-income Minnesotans, saying it would help small business owners, self-employed workers, and undocumented immigrants.

[84] Internal documents showed he had exchanged emails with the lab's head, Ellen Anderson, who was also a former DFL state senator, about creating the position months before it was publicly posted.

[84] The documents were requested by Republican state representative Chris Swedzinski, who sent a letter to House Speaker Melissa Hortman saying "there is no question that Rep. Long would not have been hired but for his position as a lawmaker".

[86] She also disclosed that she had previously been employed by the university, and taught classes alongside Anderson, and asked for House nonpartisan research to retain outside counsel to look into the matter.