Senate Majority Leader John Thune (R-SD) is forging a close working relationship with President-elect Donald Trump, one that the new GOP leader sees as critical for the success of a Republican-controlled Washington.

Donald Trump and his GOP allies in Congress have recently shared some of the first details of their ambitious agenda — sweeping tax cuts, border security and raising the debt limit — which they hope to muscle through in the first 100 days of the president-elect’s term.

President-elect Trump’s public back-and-forth over whether Republicans should pass his agenda in one or two massive packages is deepening the disagreements among lawmakers over how to tackle the ambitious undertaking.