Republican candidate Richard Tisei reserved almost $650,000 of advertising time on cable and broadcast television for the last month of his competitive race against Rep. John Tierney (D).

Tisei, a former state Senator and 2010 nominee for lieutenant governor, reserved time on cable stations from Oct. 9 to 15. And he reserved time on both cable and Boston broadcast stations from Oct. 16 through Election Day.

Both the Democratic Congressional Campaign Committee and the National Republican Congressional Committee have reserved millions of dollars in airtime in the Boston media market, some or all of which could be used in the 6th district race.

“This is a substantial buy for the final four weeks of the campaign,” Tisei campaign manager Paul Moore said in a statement to Roll Call. “It will ensure Richard’s ability to connect with the voters, who are looking for an independent-minded, problem-solving, effective Congressman.”

Tisei outraised Tierney in the past two fundraising quarters. At the end of March, Tisei had $455,000 in cash on hand; Tierney had $795,000.

“We’re looking forward to a vigorous debate this fall,” Tierney campaign manager Matt Robison said. “[T]his will be a choice between John Tierney’s record of fighting for the middle class versus Richard Tisei’s support for this right-wing Republican Congress and its agenda of raising taxes on the middle class to fund tax cuts for the wealthy.”

Roll Call rates the race as Leans Democratic.