The Note's Must-Reads are a round-up of today's political headlines and stories from ABC News and the top U.S. newspapers. Posted Monday through Friday right here at www.abcnews.com

Compiled by ABC News' Jayce Henderson, Amanda VanAllen, Carrie Halperin, and Erin McLaughlin

PRESIDENT OBAMA: USA Today's Catalina Camia: " Poll: Obama expands national lead over GOP rivals" President Obama has widened his lead over Mitt Romney and Rick Santorum to double digits in a new national poll by CNN. In the hypothetical match-ups, 54% of registered voters would back Obama compared with 43% for Romney. LINK

MITT ROMNEY: ABC News' Michael Falcone, Emily Friedman and Matthew Jaffe: " Marco Rubio Endorses Mitt Romney, Avoids Vice Presidential Speculation" Florida Sen. Marco Rubio officially threw his support behind Republican presidential candidate Mitt Romney Wednesday night in an appearance on Fox News' "Hannity" show. "It's evidently and increasingly clear that Mitt Romney's going to be the Republican nominee," Rubio told Sean Hannity. LINK

The Wall Street Journal's Sara Murray: " George H.W. Bush to Endorse Romney" George H.W. Bush will officially endorse Mitt Romney in an event at the former president's office in Houston Thursday. Mr. Bush has offered implicit support for Mr. Romney in the past but his formal endorsement marks the latest in a string of establishment Republicans coalescing behind the former Massachusetts governor. LINK

The Washington Times' Seth McLaughlin: " Romney rivals seen 'tilting at windmills' in convention ploy" A sneak attack at the convention, the plan that Newt Gingrich and Rick Santorum are counting on to win the Republican presidential nomination, is far-fetched in the eyes of state party officials who say that Mitt Romney will be nominated even if he goes into the convention with only a plurality of delegates. LINK

The New York Daily News' Jonathan Lemire: " Mitt Romney plans 11,062-square-foot oceanfront palace outside San Diego" If Mitt Romney is elected President, the White House would be his smaller, "other" home - the one without the ocean view.New details about the GOP front-runner's plans to knock down his current California beach house and build an opulent new estate are emerging - and they're complete with a separate elevator just for his family's cars. LINK

The Hill's Jamie Klatell: " Rubio endorses Romney for GOP presidential nod" Sen. Marco Rubio (R-Fla.) endorsed Mitt Romney on Wednesday in the race for the GOP presidential nomination. "I am going to endorse Mitt Romney," the freshman senator said on Fox News. "Not only is he going to be the Republican nominee, but he offers a stark contrast to this president's record." LINK

Bloomberg's David J. Lynch: " Romney Thrived at Harvard as He Mocks Obama Tie to School" Mitt Romney likes to take jabs at President Barack Obama for representing the values of the Harvard faculty lounge. He should know.  Like the president, the former Massachusetts governor is a graduate of Harvard Law School. Unlike the commander-in-chief, Romney also has a second Harvard graduate degree, in business. LINK

RICK SANTORUM: The New York Times' Jeremy Peters: " Taking Heed of Criticism, Santorum Tones Down Attacks" Rick Santorum has eased up on using phrases like" worst Republican in the country" when tearing into Mitt Romney. And he is no longer saying that a vote for Mr. Romney would be basically the same thing as a vote for President Obama. LINK

The Washington Post's Sandhya Somashekhar: " Rick Santorum's nice-guy persona is turning a bit testy lately" For a while, it had seemed that Rick Santorum's crabby days were behind him. Gone were the sarcastic potshots at reporters and peevish outbursts aimed at his political opponents. He had transformed into the Mr. Rogers of the presidential race: good-natured, self-deprecating and downright likable. LINK

NEWT GINGRICH: ABC News' Amy Bingham and Karen Travers: " Newt Gingrich: How Long Can Bruised Candidate Hang On?" Newt Gingrich is battered and his fundraisers are bruised, but the former House speaker is not giving up.  With a fifth as many delegates as GOP frontrunner Mitt Romney, 12 percent support nationally in the latest Gallup poll and a "very tight" budget to run on for another four months, Gingrich's campaign seems to be hanging on by a thread. LINK

Politico's Jonathan Martin and Alexander Burns: " Gingrich puts political legacy at risk" Seeking the presidency at 68, Newt Gingrich envisioned himself as a latter-day Churchill, returning triumphantly from the political wilderness to lead his country at an hour of peril. He got part of the story right. His White House bid had all the makings of an improbable comeback, but it's now coming to a far more ignominious end than he imagined, a finish that risks tarnishing his political legacy. LINK

ABC NEWS VIDEOS: " Mitt Romney on Fight Songs and Plant Closings" LINK

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