One thing the recent collapse of healthcare reform efforts in the House of Representatives has revealed is just how quickly attitudes and alliances can shift in Washington, DC. Last year Mr Trump and members of the House Freedom Caucus, a collection of 30 or so libertarian-leaning fiscal conservatives in Congress, were singing from the same anti-government hymnal. Now, however, Mr Trump is the government - and he teamed up with congressional leadership to back a healthcare bill that conservative hard-liners believe didn't go far enough in undoing the 2009 Democratic-designed system. The effort's failure set off back-and-forth sniping between Mr Trump and the Freedom Caucus that morphed into a classic insider-outsider faceoff, with Mr Trump cast as the new voice of the powers that be. Freedom Caucus - Do these 29 white men run America? Congressman Justin Amash said the White House has become part of the hated status quo - the "Trumpstablishment", he called it in a Saturday tweet.

The former Indiana governor is charged with leading the team deciding the key appointments in the new administration.

MeHe is a favourite among social conservatives who boasts considerable experience in Washington.

Mr Pence was raised Roman Catholic along with his five siblings in Columbus, Indiana, and says he was inspired by liberal icons John F Kennedy and Martin Luther King Jr.

He is known for his staunch opposition to abortion, signing a bill in March to ban abortion in Indiana on the basis of disability, gender or race of the foetus.

He has said he would favour overturning a 1973 Supreme Court judgement, often referred to as the Roe v Wade case, which bars the US government from prohibiting abortions.

Women's rights advocates have mounted online campaigns against his views, including asking people to call his office to tell them about their periods or to make donations to family-planning organisations in Mr Pence's name.

He served as the chair of the House Republican Conference, the third highest-ranking Republican leadership position.

He also chaired the Republican Study Group, a coalition of conservative House Republicans, which could give him a boost with some evangelicals of the party that have questioned Mr Trump's ideological purity, the BBC's Anthony Zurcher says.

Who is Mike Pence?