Frank joined Governor Bill Owens' administration in 2000, serving as a division legislative liaison and as assistant director for Water for the Colorado Department of Natural Resources.

[6] McNulty sponsored legislation to extend in-state tuition benefits to active duty military personnel on temporary assignment in Colorado and their families.

[9] McNulty's bill to create mandatory minimum sentences for criminals convicted of violent sex assaults against children died in the House Judiciary Committee.

[citation needed] Other legislation introduced and passed by McNulty included a bill to make it easier for farmers and ranchers to temporarily donate their water to help protect the environment, especially during times of drought.

He also addressed minimum bond requirements designed to keep drug dealers off the streets and pushed for divestment of state pension funds from companies doing business in Iran, a move which led to new rules governing Colorado's Public Employees Retirement Association investments.

[16] In 2008, McNulty successfully secured a second term in the Colorado House of Representatives; earning 63% of the votes cast in the general election against the Democratic nominee, John Stevens.

He initiated efforts to help protect children from coming into contact with felons while attending public schools and worked with Rep. Laura Bradford and Rep. Scott Tipton to resurrect Jessica's Law.

After House Minority Leader Mike May of Parker announced his intention to retire in December 2008, McNulty was identified as a potential candidate for the vacated leadership post.

McNulty secured a third term in the Colorado House of Representatives in 2008, earning 67% of the votes cast in the general election against the Democratic nominee, Gary Semro.

[29][30] The 2012 General Election also witnessed President Obama capture Colorado by 5.5 points over Republican Mitt Romney and the Democratic Party gained five seats in the House of Representatives, which gave them a majority.