President Donald Trump smiles at Secretary of State Rex Tillerson after he was sworn in in the Oval Office of the White House in Washington, Feb. 1, 2017.
President Donald Trump smiles at Secretary of State Rex Tillerson after he was sworn in in the Oval Office of the White House in Washington, Feb. 1, 2017.

Rex Tillerson was sworn-in Wednesday night as the new U.S. secretary of state, hours after his confirmation by the U.S. Senate.

Vice President Mike Pence gave the oath to Tillerson in the Oval Office of the White House as President Donald Trump looked on.

Tillerson thanked Trump for giving him what he called an "enormous opportunity," and said he will always serve the interests of the American people at all times.

WATCH: Tillerson thanks Trump for 'enormous opportunity'

Trump congratulated Tillerson, saying the new secretary is respected all over the world and will bring his unique skills and great insight into global diplomacy.

Only three Democrats and one Independent joined a united Republican caucus in backing Tillerson, who was confirmed by a vote of 56-43 after senators of both parties spent weeks mulling the ExxonMobil CEO’s cozy relationship with Russian President Vladimir Putin and his ability to put business interests aside and serve as America’s top diplomat.

Watch: Republican-dominated Senate Backs Trump's Cabinet Picks

“He [Tillerson] has done a tremendous job for one of the largest businesses in the world,” said Senator John Cornyn, a Texas Republican. “Now, his enormous experience, aptitude and talent are going to be put to work for the American people.”

However, Democratic Senator Ben Cardin of Maryland said, “I remain concerned that Mr. Tillerson’s demonstrated business orientation would prevent him from being a secretary of state who forcefully advances the values and ideals that have defined our country."

Cardin added that Tillerson will be asked to carry out Trump’s “dangerous and reckless foreign policy.”

FILE - Senate Foreign Relations Committee Chairman
FILE - Senate Foreign Relations Committee Chairman Bob Corker, left, listens as Sen. Ben Cardin speaks during a committee business meeting on the nomination of Rex Tillerson to be secretary of state, Jan. 23, 2017 in Washington.


Cabinet choices

Meanwhile, the Senate also advanced three other Cabinet picks on Wednesday, as Republicans overcame dogged and, at times, unprecedented delay tactics by Democrats by taking unprecedented steps of their own.

Senate committees advanced the president’s nominees for attorney general, treasury secretary, and health and human services secretary with Republican votes alone.

The Judiciary Committee supported Republican Senator Jeff Sessions to become America’s chief law enforcement officer 11-9, with all Republicans voting in favor and all Democrats opposed.

Republican Senator Mike Lee of Utah described Sessions as “a man who has devoted his entire life to the law – to enforcing it, to protecting it, to defending it and, as a lawmaker, to improving it.”

“Senator Sessions, although an amiable colleague, is well outside the mainstream of both Democratic and Republican positions on criminal justice reform, torture, privacy, and voting rights,” said Senator Chris Coons, a Democrat from Delaware.

FILE - Attorney General-designate Sen. Jeff Sessio
FILE - Attorney General-designate Sen. Jeff Sessions takes his seat on Capitol Hill in Washington, Jan. 10, 2017, after a break in his confirmation hearing before the Senate Judiciary Committee.


Democrats delayed votes on multiple nominees by invoking arcane Senate rules and exercising procedural tactics whenever possible. Tillerson’s confirmation was set back more than a week when Democrats insisted on a preliminary vote ahead of final confirmation, and did so after having invoked a rule that delays a floor votes on a nominee.

Sessions would have been approved in committee Tuesday, but Democrats invoked a little-used rule limiting the length of time a committee can meet, then spoke at length in the Judiciary Committee, ensuring the time limit would be reached before a vote could be held.

Boycotted meeting

Rarer yet, Democrats boycotted the Finance Committee Tuesday and Wednesday to forestall votes on Steve Mnuchin, the treasury secretary nominee, and Tom Price, nominee for health and human services secretary.

Senate rules require at least one minority member be present for committee votes to proceed. A visibly frustrated Finance Committee chairman, Senator Orrin Hatch of Utah, led a successful effort to change the rules governing the panel, and Mnuchin and Price were swiftly approved with Republican-only votes.

Senate Health, Education, Labor and Pensions Commi
FILE - Senate Health, Education, Labor and Pensions Committee member Sen. Orrin Hatch, center, leaves the committee's executive session on Education Secretary-designate Betsy DeVos, on Capitol Hill in Washington, Jan. 31, 2017.


“The only chaos we have in the Senate is because of Senate Democrats,” said Majority Leader Mitch McConnell, a Kentucky Republican. “It is time [for Democrats] to get over the fact that they lost the election. The president is entitled to have his Cabinet appointments considered.”

Democrats insist extra time to consider Trump’s nominees is needed.

“The proposed Trump domestic Cabinet is an unprecedented swamp of conflicts of interest, failures of disclosure, and dark money secrets,” said Senator Sheldon Whitehouse of Rhode Island. “None of this is good.”

Shortened tempers and frayed nerves have been evident in a body that prides itself on decorum and lofty debate. Hatch said Democrats were acting “like idiots,” while Cornyn blasted Democratic delay tactics as “a hissy fit.”

Focusing on Trump

Democrats, meanwhile, focused their firepower on the president.

“The opening days of this administration have been a Gong Show, but a Gong Show with a nuclear button,” Whitehouse said. “His [Trump’s] incompetence is a threat to all around him. To say that it is amateur hour at the White House is to slander amateurs.

FILE - Senate Judiciary Committee member Sen. Shel
FILE - Senate Judiciary Committee member Sen. Sheldon Whitehouse makes a statement on Capitol Hill in Washington, Jan. 11, 2017. It was the second day of a confirmation hearing for Attorney General-designate Sen. Jeff Sessions, R-Ala.

“This dangerous state of affairs puts all of Trump’s nominees in a new light,” he added.

But the ire of recent days could be dwarfed by the fury of a looming battle over Trump’s Supreme Court nominee, appellate court Judge Neil Gorsuch.

Unlike Trump’s Cabinet picks, Democrats could both delay and block Gorsuch’s nomination. Republicans, who control the chamber, could change Senate rules that currently allow the minority party to insist on a three-fifths majority to confirm Supreme Court nominees.

A rules change has been called “the nuclear option” as it would forever alter the Senate, a body where the minority party historically has been able to curb the ambitions of the majority.