Shortly after the Senate convened at noon and voted to confirm Elad Roisman to be a member of the Securities and Exchange Commission, Vice President Mike Pence swore in Kyl, a former Senate minority whip who retired in 2013 but was appointed on Tuesday to fill the vacancy caused by the death of Sen. John McCain, R-Ariz.
The Senate now has 51 Republicans, 47 Democrats and two independents who caucus with Democrats.
A few hours later, Balderson, who won a special election in Ohio last month to replace Republican Pat Tiberi (who left his seat in January to take a job in the private sector) took the oath of office as a member of the House.
The House now has 237 Republicans and 193 Democrats. There are five vacancies: Pennsylvania 7th (Pat Meehan resigned), Pennsylvania 15th (Charlie Dent resigned), Oklahoma 1st (Jim Bridenstine left when he was confirmed as NASA administrator), New York 25th (Louise Slaughter, who died) and Michigan 13th (John Conyers Jr., who resigned).
Paul Fontelo contributed to this report.