In four weeks since House launched inquiry into president, he has taken steps in various fields repeatedly testing loyalty of his stalwart Republican allies

Crowded together onstage, candidates snipe at each others' policies on taxation but stand united on impeachment for Trump

NY Times says federal prosecutors have launched a probe into Giuliani's dealings in Ukraine, including efforts to undermine ex-envoy Marie Yovanovitch

Former VP says US president has 'betrayed his nation,' marking a much tougher stance from Democratic White House hopeful who is now neck and neck with Elizabeth Warren in race

President tweets that he won't allow ambassador to testify before 'a totally compromised kangaroo court;' Schiff calls move further evidence of obstruction of Congress

New source said to corroborate original informant's complaint about Trump's efforts to pressure Ukraine into investigating former vice president Joe Biden

At center of Naftogaz plan are two Soviet-born Florida real estate entrepreneurs, Lev Parnas and Igor Fruman, and an oil magnate from Boca Raton, Harry Sargeant III

Facing impeachment proceedings after asking Ukraine to probe his chief political rival, US president tells reporters Beijing should do the same

US vice president, a key intermediary between White House and Ukraine, has until now rarely been drawn into Trump controversies

US president’s attacks come amid escalating impeachment fight over his effort to pressure the government of Ukraine to investigate Biden