Rob Portman and John Kasich

In this Nov. 1, 2010 file photo, Rob Portman, center, and John Kasich, right, rally together with then-U.S. Rep. John Boehner of Ohio. Portman and Kasich won their respective races for U.S. Senate and governor the following day.

(Al Behrman, The Associated Press)

CLEVELAND, Ohio - U.S. Sen. Rob Portman endorsed Gov. John Kasich for president Saturday, calling him a "leader who has a proven record of delivering results."

Portman will serve as a national co-chair of Kasich's campaign.

News of the endorsement trickled out late Friday night, when sources close to Kasich and Portman confirmed to cleveland.com that an announcement was imminent.

On the surface, such a development might not seem surprising. Top Ohio Republican backs another top Ohio Republican. That's how it always works, no?

In most cases you would be correct. But Portman's case is somewhat special.

Consider that he served in the White House under President George H.W. Bush and later returned for two high-profile posts under President George W. Bush. Family loyalties might have compelled Portman to get behind Jeb Bush's candidacy.

Consider that several past Portman aides are working to elect Marco Rubio. Perhaps Portman pondered joining forces with his Senate colleague from Florida. Then there is Ben Carson, who until last week had a longtime Portman adviser running his campaign.

To put it another way, Portman's backing never was a slam-dunk.

With the exception of Treasurer Josh Mandel, who is Rubio's top supporter in Ohio, before Saturday every other Republican officeholder elected statewide already had endorsed Kasich's bid. Portman's neutrality fueled quiet speculation.

Maybe he favored Kasich but didn't want to upset his patrons in the Bush family. Or maybe Portman preferred Bush but didn't want to embarrass Kasich.

Portman's tough re-election race this fall also might be a factor. It cuts both ways, though.

Picking a favorite now could upset national Republicans who could be helpful to Portman this year. But a popular governor - Kasich recently has enjoyed record-high approval ratings in Ohio - could be helpful to Portman, too. So could the governor's allies at the Ohio GOP, which voted Friday to endorse Kasich. Not that their support ever was in doubt.

In his endorsement of Kasich, Portman took a shot at former Gov. Ted Strickland, the senator's likely Democratic challenger this fall.

"John turned Ohio around at a tough time and I believe he can do the same for our country," Portman said. "John inherited a mess from former Governor Ted Strickland. Under Governor Strickland, Ohio lost over 350,000 jobs and ranked 48th in job creation, as companies left Ohio for other states."

A Strickland campaign spokesman later fired back, calling Portman a Washington "insider" who "always puts the interests of the D.C. establishment over Ohio's working people."

By coming out publicly for Kasich now, Portman gives Kasich a well-timed boost. The New Hampshire primary is one month from Saturday. Bush and Kasich are among the cluster of center-right establishment candidates fighting for second place there.

Portman is a fixture of that center-right establishment, a pragmatic conservative who was on Mitt Romney's short list for vice president four years ago. He is a skilled fundraiser and weighed his own presidential bid for 2016. He is a Dartmouth College alum, meaning some New Hampshire stumping might be on the agenda. And he remains close with Romney, who has yet to endorse a candidate.

(Worth noting: The Washington Post reported this week that when Romney was weighing another run for president, he privately consulted with Portman.)

Fair or not, many will see Portman's decision to get off the sidelines as a statement against Bush. Sure, many also will see Portman's choice of Kasich as fait accompli.

But Portman has shown he can be tremendously helpful to his allies. He campaigned relentlessly for Romney in 2012 and for Senate Republicans in 2014.

The true value in his endorsement will be in how much Portman does for Kasich.