Senate Minority Leader Mitch McConnell 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 (R-Ky.) 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.

As the head of the Republican National Convention, Boehner had resisted backing any of the GOP primary candidates, growing even more reluctant to address the issue in late January and February when their was a stronger chance that neither Romney nor any other candidate would clear the minimum hurdle to secure the nomination.

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.

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

Boehner and McConnell. (Win McNamee/GETTY IMAGES)

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.