Coming off a sweep in the Potomac Primaries, John McCain's campaign has a message for Mike Huckabee: It's over.

The campaign released a memo after McCain won Virginia, Maryland and the District of Columbia Tuesday night saying the victories make it "mathematically impossible for Governor Huckabee to secure the Republican nomination for president."

As he pressures Huckabee, McCain is resuming the role of presumptive nominee after suffering embarrassing losses to his rival Saturday in Kansas and Louisiana. McCain has clenched that mantle since Super Tuesday, and was emboldened after Mitt Romney dropped out of the race last week.

He's since set to marshaling the support of the Republican base, and mending fences with those leaders with whom he's clashed in the past.

The House Republican leadership -- including House Minority Leader John Boehner and GOP Whip Roy Blunt -- endorsed McCain Wednesday.

There McCain said Huckabee "has every right to stay in this race for as long as he wants to and I will respect that."

"I don't pretend that I wouldn't like Governor Huckabee not in the race, but I respect his commitment to do so, and his commitment to continuing the race," he said. "Of course I'd like for him to withdraw today. It would be much easier. But I ... respect his right to continue in this race just as long as he wants to."

The campaign has taken a stronger tone.

"With only 774 delegates left on the table after tonight, Governor Huckabee cannot win the Republican nomination for president," campaign manager Rick Davis said in the memo.

Though Associated Press tallies showed there were 994 delegates remaining, more than 200 of those are from contests that have already happened. The McCain campaign was referring to 774 delegates up for grabs in remaining contests.

But either balance would be daunting for Huckabee to close.

According to the latest AP tallies, Huckabee has 241 delegates to McCain's 821. That means the former Arkansas governor needs 950 more delegates to reach the 1,191 needed to clinch the nomination, and McCain needs about 370.

McCain commended Huckabee for running a "formidable" campaign Tuesday night, saying "he certainly keeps things interesting."

Huckabee has said repeatedly he would be staying in the race until one candidate has 1,191 delegates.

He teased the pundits Tuesday evening in Little Rock, Ark.

"On one hand, you have the pundits saying that I'm really not a factor, and on the other hand, boy, I'm gonna make it really hard for John McCain," he said. "Well, it can't be both, you gotta pick one or the other, so pick which one it is: If I'm a significant factor that's really messing it up for him or if I'm an absolute insignificant irritation and just sort of an aside. But I can't be both things at the same time. That's not possible."

FOX News' Mosheh Oinounou contributed to this report.