A political nonprofit supportive of President Trump is running television ads in key states to preserve votes for the Republican tax reform legislation as House and Senate negotiators attempt to reconcile competing bills.

45Committee, backed by Republican donors and active on behalf of Trump and his legislative agenda, is running new spots in Arizona, Maine, and Wisconsin thanking Republican senators from those states for voting to advance the GOP tax reform package to a conference committee. Republican Sens. Jeff Flake of Arizona, Susan Collins of Maine, and Ron Johnson of Wisconsin had threatened to vote against the bill but came around after securing changes.

"Arizona has a proud history of courageous, conservative leaders," the voiceover says as the advertisement running on broadcast and cable in the Phoenix media market opens. "Thank Sen. Flake for voting yes on tax reform."

The ad buy is part of a multi-million dollar investment 45Committee has sunk into helping Trump and the Republican Congress pass the first tax reform package in three decades. Spots also are running in the Milwaukee and Madison markets, in Wisconsin, and the Bangor, Portland, and Presque Isle markets, in Maine.

The House and Senate have both approved version of a federal tax overhaul. A panel made up of House and Senate negotiators from both parties, driven by the Republicans, is attempting to bridge the differences between them in time to set up a pre-Christmas vote on a compromise package.

Senate Republicans passed their bill by a very slim margin, and will need to keep almost all of their members on board to pass the conference committee's adjusted bill.