House Speaker John Boehner, along with Senate Minority Leader Mitch McConnell, has endorsed the former Massachusetts governor for president. (Mark Wilson/GETTY IMAGES)

Senate Minority Leader Mitch McConnell (R-Ky.) on Tuesday seconded the House speaker’s earlier endorsement of Mitt Romney as the GOP’s presidential nominee, saying that the Republican Party is “unifying” behind the former Massachusetts governor.

"We're all behind him," McConnell told reporters in the afternoon, predicting an "incredibly close, hard-fought campaign."

Earlier in the day, House Speaker John A. Boehner (R-Ohio) pledged his full support to Romney’s presidential campaign, saying that it would “contrast sharply” with President Obama’s in the November election.

“I will be proud to support Mitt Romney,” Boehner said.

Mitt Romney and Rep. Paul Ryan during the Wisconsin Republican primary this month. Ryan endorsed Romney, who won the primary. (Scott Olson/GETTY IMAGES)

McConnell had also remained neutral during the primary.

But on Tuesday morning, Boehner told reporters that “Mitt Romney is going to be our nominee.” He made the announcement after the Republican Conference’s first meeting since a two-week spring break.

Boehner and Senate Minority Leader Mitch McConnell are “uniting” behind Romney. (Win McNamee/GETTY IMAGES)

“I will be proud to support Mitt Romney,” Boehner said.

McConnell is the 102nd member of Congress to throw his support behind the presumptive Republican nominee.

Even before Romney’s toughest GOP rival, Rick Santorum, withdrew from the race last week, some congressional leaders had already begun consulting the Romney camp in Boston. Rep. Paul Ryan (R-Wis.), who would later endorse Romney before his home state held its Republican primary, had several conversations with Romney before Ryan unveiled his austerity budget last month. The blueprint includes tax cuts, deep spending cuts for agencies and entitlement programs and Medicare reforms — all of which have drawn severe criticism from Democrats and others. Romney signed off on the thrust of those key proposals.