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, Will Cantine and Jordan Mazza

VICE PRESIDENT BIDEN The Hill's Julian Pecquet: " Biden goes on mission to China" Vice President Biden has been thrust into the center of an escalating standoff with China that is testing him on the global stage ahead of a possible presidential run in 2016. President Obama dispatched Biden to Asia, where he will deliver a strong warning to China for declaring an air defense zone over islands that are also claimed by U.S. ally Japan. "This is an opportunity for Vice President Biden to raise our concerns directly with policymakers in Beijing and to seek clarity regarding the Chinese intentions in making this move at this time," White House spokesman Jay Carney said Monday. "We do not accept the legitimacy of China's requirements." LINK

HEALTH CARE ABC News' Devin Dwyer and Mary Bruce: " New Obamacare Headache: Is Your Enrollment Real?" Bob Shlora of Alpharetta, Ga., was supposed to be a belated Obamacare success story. After weeks of trying, the 61-year-old told ABC News he fully enrolled in a new health insurance plan through the federal marketplace over the weekend, and received a Humana policy ID number to prove it. But two days later, his insurer has no record of the transaction, Shlora said, even though his account on the government website indicates that he has a plan. LINK

USA Today's Kelly Kennedy: " Government says it fixed bug slowing insurance sign-up" Government says it fixed bug slowing insurance sign-up A software bug that caused 80% of the problems with information forms insurers received from the HealthCare.gov website has been fixed, the Centers for Medicare and Medicaid Services announced Monday. "That bug has been fixed and is now working properly," said Julie Bataille, the CMS communication director. LINK

The New York Times' Sheryl Gay Stolberg: " A New Wave Of Challenges To Health Law" More than a year after the Supreme Court upheld the central provision of President Obama's health care overhaul, a fresh wave of legal challenges to the law is playing out in courtrooms as conservative critics - joined by their Republican allies on Capitol Hill - make the case that Mr. Obama has overstepped his authority in applying it. A federal judge in the District of Columbia will hear oral arguments on Tuesday in one of several cases brought by states including Indiana and Oklahoma, along with business owners and individual consumers, who say that the law does not grant the Internal Revenue Service authority to provide tax credits or subsidies to people who buy insurance through the federal exchange. LINK

The Washington Post's Amy Goldstein and Juliet Eilperin: " Health-Care Enrollment On Web Plagued by Bugs" The enrollment records for a significant portion of the Americans who have chosen health plans through the online federal insurance marketplace contain errors - generated by the computer system - that mean they might not get the coverage they're expecting next month. The errors cumulatively have affected roughly one-third of the people who have signed up for health plans since Oct. 1, according to two government and health-care industry officials. The White House disputed the figure but declined to provide its own. LINK

Politico's Carrie Budoff Brown and Jonathan Allen: " White House Returns To Obamacare Sales Mode" President Barack Obama will launch a coordinated campaign Tuesday by the White House, congressional Democrats and their outside allies to return attention to why the Affordable Care Act passed in the first place. After two months of intense coverage of the botched HealthCare.gov rollout, the president will host a White House event kicking off a three-week drive to refocus the public on the law's benefits, senior administration officials told POLITICO. LINK

Bloomberg's Alex Wayne and Alex Nussbaum: " Stakes for Obamacare Raised by U.S. Report Goals are Met" A day after President Barack Obama raised the stakes on his three-year-old health-care overhaul by declaring his online insurance exchange fixed, more than 800,000 people will test the website's capabilities. Healthcare.gov had 375,000 visitors today by noon New York time, Julie Bataille, a spokeswoman for the Centers for Medicare & Medicaid Services, said on a conference call with reporters. The agency expects to surpass 800,000 users by day's end. LINK

CONGRESS The Los Angeles Times' Lisa Mascaro: " Gridlock in Congress could leave millions hurting over the holidays" Congress' unfinished business threatens to leave millions of Americans - including the unemployed, Pentagon contractors and even supermarket shoppers - in the lurch this holiday season. With partisan dysfunction unlikely to subside in coming weeks, lawmakers appear ready to punt several issues into the new year. But many Americans could start feeling the effects of inaction as early as this month. LINK

ECONOMY The Wall Street Journal's David Wessel: " Why Does Economy Grow More Under Democratic Presidents?" The U.S. economy has performed better since World War II when the president is a Democrat rather than a Republican, two prominent Princeton University economists conclude. The reasons, they say, involve more luck than successful policies. Over the past 64 years and 16 presidential terms, the U.S. grew at an average rate of 4.35% when a Democrat was in the White House and at a 2.54% when a Republican was, a gap the economists call "astoundingly large." LINK

IRS The Washington Times' Stephen Dinan: " Lawmakers suspect FBI is impeding IRS inquiry, targeting conservative groups" The House's chief investigator says the FBI is stonewalling his inquiry into whether the agency and the Internal Revenue Service targeted conservative group True the Vote for special scrutiny, and Rep Darrell E. Issa is now threatening subpoenas to pry loose the information from FBI Director James B. Comey Jr California Republican, and Rep. Jim Jordan Ohio Republican, are leading the House Oversight and Government Reform Committee's IRS inquiry. LINK

REGIONAL / TRAIN DERAILMENT New York Daily News' Erin Durkin and Adam Edelman: " Mayor Bloomberg spotted golfing in Bermuda during Metro-North derailment" Mayor Bloomberg was hitting the links in Bermuda Sunday when a commuter train derailed in the Bronx and killed four people - and he didn't exactly rush back. Bloomberg was playing golf at the luxurious Mid Ocean Club - and didn't leave the course until more than four hours after the 7:20 a.m. train tragedy, The Wall Street Journal first reported Monday, citing a person who saw the mayor. Asked Monday if he was in Bermuda when the wreck occurred, Bloomberg skirted the issue. LINK

ABC NEWS VIDEO " President Obama Observes World AIDS Day" LINK

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