AP

WASHINGTON MITT Romney’s status has shifted from front-runner to near-certain Republican nominee in what has been an extended and politically bloody fight to challenge President Barack Obama in the November election.

Second-place Rick Santorum seemed to publicly acknowledge for the first time on Wednesday that his quest for the presidential nomination may end in failure, and third-place Newt Gingrich is running out of money and cutting back his campaign, both in staff and appearances.

Romney aides were eagerly promoting an expected formal endorsement Thursday by former President George H W Bush, although they declined to say whether Bush had been asked for a public show of support.

Bush’s son, George W Bush, was generally viewed as the more conservative president of the two, but his popularity has waned among Republicans since the bottom fell out of the economy in 2008, and he has kept a low profile in this presidential race. Romney picked up another key endorsement Wednesday night from Republican Senator Marco Rubio of Florida, a key Hispanic leader who said it’s increasingly clear that Romney will win the nomination.

Like others in the Republican establishment lining up behind former Massachusetts governor Romney, Rubio said continuing the primary fight will only damage the effort to defeat Obama. Rubio said he’s convinced that Romney will govern as a conservative.

Romney has been dogged in this campaign by questions about his past, more moderate stances on key social issues such as abortion and by Santorum’s popularity with conservatives.

But Romney is far ahead in picking up the needed delegates to win the nomination at the party’s conference in August. An Associated Press count has showed Romney with 568 delegates and on a pace to reach the required 1,144 in the remaining primary and caucus states.

Santorum has 273, and Gingrich 135.

The next Republican primary contests are Tuesday in the District of Columbia and the Midwestern state of Wisconsin. A Marquette University poll shows Romney as having overtaken Santorum in the state by an 8-point margin, 39-31.

Wisconsin is Santorum’s last chance to keep alive his claim that he can go toe-totoe with Obama in the industrial heartland.