George H.W. Bush stood shoulder to shoulder with John McCain on Monday, offering an endorsement to the presumptive Republican presidential nominee.

Mathematically, statistically, symbolically and politically, McCain is just inches from winning the nomination, and the former president's endorsement offers a signal that the Republican powerhouse family is coalescing around the candidate. Former Florida Gov. Jeb Bush has already endorsed McCain for president.

"I did not come here to tell any other candidate what to do, a very wise man once said influence is something you always have until you actually try to exert it," Bush said from the Houston Hobby Airport in Texas, where he was joined by his wife, Barbara.

"Now is the right time for me to help John in his effort to start building the broad base coalition it will take for our conservative values to carry the White House this fall. His character was forged in the crucible of war. His commitment to America is beyond any doubt, but most importantly he has the right values and experience to guide our nation forward at this historic moment," said the former president.

"I think that President Bush's endorsement honors me, I believe it will help us enormously in that process of uniting our party as we move forward," McCain said with his wife, Cindy, by his side. "President Bush, Barbara, I can ensure you that Cindy and I will do everything we can to make sure that you are proud and that your support of our candidacy will be something that you can look back on as having been the right thing to do."

McCain campaign officials say they expect the current President Bush to endorse the candidate once he has numerically clinched the nomination.

Asked whether he thinks the Bush endorsement spells the end of his campaign, Mike Huckabee said endorsements don't speak for the base.

"Does his voice count more than the millions of Republicans across the country? Blue-collar Republicans that maybe don't have platform he has? Do their votes not matter? Do the people who have been coming to our rallies suddenly just say ... 'someone else from the party establishment has spoken let's just give up and not be heard from'? That's not how elections are supposed to work" the former Arkansas governor said while campaigning in Wisconsin.

But McCain campaign officials are working on a plan to build the national organization for a general election.

Still, five or six senior campaign insiders spent the weekend at the senator's ranch in Sedona, Ariz., to hold a private powwow on who they should hire for that campaign; what their national electoral college map should be; how best to use President George W. Bush on the stump in terms of fundraising and campaigning; which members of Congress McCain needs to court and spend time with; and who McCain will stump for on the campaign trail.

But most pressing among those questions is how they will craft a strategy for the Democratic nominee, who is undetermined at this time. The campaign is beginning to develop to competing scenarios to challenge either Barack Obama or Hillary Clinton.

For McCain, among his biggest challenges will be to fend off from either Democratic candidate claims that a McCain victory would amount to a third Bush term. Speaking Sunday, McCain said he has been a critic of the Bush administration's conduct of the war, and pointed to fighting global warming and wasteful government spending as two major differences between him and the current president.

FOX News' Carl Cameron contributed to this report.