Democrat Niki Tsongas will be sworn in as the newest Member of Congress Thursday morning after winning the special election in Massachusetts’ 5th Congressional district Tuesday night, beating Republican Jim Ogonowski by 6 points.

According to unofficial results from the secretary of state’s office, Tsongas, the widow of former Sen. Paul Tsongas (D), received 51 percent and Ogonowski received 45 percent in the closer-than-expected race for the seat vacated in July by Rep. Marty Meehan (D).

“I’d like to thank the voters of the 5th district for giving me the honor of representing them in Congress,” said Tsongas in her remarks as prepared for delivery. “We have a remarkable legacy in this district — from Edith Nourse Rogers to Paul Tsongas to Marty Meehan. It is my great honor that you have chosen to add my name to theirs and I will not let you down.”

Turnout figures were not available yet from state officials, although 105,985 people voted in Tuesday’s special election. More than twice that figure — 216,823 people — voted in the 2006 general election. Automated polls leading up to the general election showed Tsongas with a 10-point lead.

National Republican Congressional Committee Chairman Tom Cole (Okla.) hailed the results in blue-state Massachusetts as proof that voters are “angry with a Democrat-led Congress.”

“Democrats have a reason to worry,” Cole said. “In a race that should have been won in a walk, Democrats were forced to funnel a massive amount of resources and dispatch an all-star cast of liberal icons at the 11th hour in order to ensure victory.”

Tsongas outspent Ogonowski by a 4-1 margin in the unexpectedly heated race for the open seat. She is the first woman elected to the Massachusetts delegation in more than 25 years.

— Shira Toeplitz